ROR Tricks from screencasts.txt

1) To use controller methods into views ---> helper_method :action_name  (Screencast - 20)

1.5) To include any helper file(helper module) in controller ---> helper :authentication (for authentication_helper.rb) (Screencast - 64)

	If u want to use any helper method provided by rails then, u can use it by calling the method on ActionController::Base.helpers 

	def description
	  "This category has #{helpers.pluralize(products.count, 'product')}."
	end

	def helpers
	  ActionController::Base.helpers
	end

    However, some of the helper methods link link_to will not be accessible on models because they depend on request object but they can be accessed on controllers which has access to request object, by using @template variable. Ex

	def create
	  @product = Product.new(params[:product])
	  if @product.save
		flash[:notice] = "Successfully created #{@template.link_to('product', @product)}."
		redirect_to products_url
	  else
		render :action => 'new'
	  end
	end

2) In the view, we can use pluralize method to display 1 or more items.
   <%= pluralize project.tasks.size, 'task' %>
   
3) In :include --> name of the association should be used .It can also be chained 
   Task.find(:all, :include => [:projects, {:comments => :user}])

   Task --> belongs_to :project, has_many :comments .  Comment ---> belongs_to :user
   
4) Use CGI::escapeHTLM(...) in controller to reject html content   
   Use CGI.escape to embed a sentence or set of words containing spaces in a URL
   url = "http://www.walmart.com/search/search-ng.do?search_constraint=0&ic=48_0&search_query=#{CGI.escape(product.name)}&Find.x=0&Find.y=0&Find=Find"
   
5) size method uses the counter cache feature of rails but length doesnot. 
   project.tasks.size --> uses counter cache
   
6) Use attr_accessible to prevent mass_assignment.    
   attr_accessible :name --> means only name can inputed using mass assignment (curl)
   
   curl -d "user[name]=hacker&user[admin]=1" http://localhost:3000/Users/
   curl -d "user[name]=hacker&user[admin]=1&user[comment_ids][]=1&user[comment_ids]=2" http://localhost:3000/users/create
   
7)  >> a = (1..12).to_a
	=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
	>> a.in_groups_of(4)
	=> [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]
	>> a.in_groups_of(3)
	=> [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12]] 

	>> a.in_groups_of(5)
	=> [[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, nil, nil, nil]]
	
	>> a.in_groups_of(5, false)
	=> [[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12]]
	>> a.in_groups_of(5, 0)
	=> [[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 0, 0, 0]]
	
8) From cmd type
   > ri strftime 
     Display the documentation (classes that have method strftime)
	 
   > ri Time.strftime
     Shows description

9) http://localhost:3000/tasks/completed == http://localhost:3000/tasks;completed (In Edgerails only / works ; doesn't)

10) Creating a rails pluggin (Railscast 33): similar to gem creation

	module StringifyTime
	  def stringify_time(*names)
		names.each do |name|
		  define_method "#{name}_string" do
			read_attribute(name).to_s(:db) unless read_attribute(name).nil?
		  end
		  
		  define_method "#{name}_string=" do |time_str|
			begin
			  write_attribute(name, Time.parse(time_str))
			rescue ArgumentError
			  instance_variable_set("@#{name}_invalid", true)
			end
		  end
		  
		  define_method "#{name}_invalid?" do
			instance_variable_get("@#{name}_invalid")
		  end
		end
	  end
	end

    read_attribute & write_attribute are methods of active record
	
11) Use form_tag to make a generic form & form_form to update a database model attributes.

12) 

<% form_tag projects_path, :method => 'get' do %>
  <p>
    <%= text_field_tag :search, params[:search] %>
    <%= submit_tag "Search" %>  === <input name="commit" type="Submit" value="Search" />
  </p>
<% end %>

The above form submit the form with URL:
http://localhost:3000/projects?search=yard&commit=Search

yard :- searched project
So to remove commit=Search from the URL write 
<%= submit_tag "Search", :name => nil %>

Then the URL becomes : http://localhost:3000/projects?search=yard

13) If you are using form_remote_for then instaed of submit_tag (if you have two submit buttons : Create & Preview) for a project, you should use submit_to_remote becoz form_remote_for serealizes the whole form and submits.

14) helper_method : capture(&block) --> returns content of block as string

15) @user.save(false)  ---> this false bypasses all model validations

16) Conditional validations :- Railscast-41
    --------------------------
	validates_presence_of :password, :if => :should_validate_password?
	validates_presence_of :country
	validates_presence_of :state, :if => :in_us?
	attr_accessor :updating_password

	def in_us?
	  country == 'US'
	end

	def should_validate_password?
	  updating_password || new_record?
	end

	# in controller
	@user.updating_password = true
	@user.save

	# or...
	@user.save(false)
	
17) with_options :-
    ---------------
	user.validates_presence_of :password, :if => :should_validate_password?
	user.validates_confirmation_of :password, :if => :should_validate_password?
	user.validates_format_of :password, :with => /^[^\s]+$/, :if => :should_validate_password?
	   ===
	with_options :if => :should_validate_password? do |user|
	  user.validates_presence_of :password
	  user.validates_confirmation_of :password
	  user.validates_format_of :password, :with => /^[^\s]+$/
	end
	
	def should_validate_password?
	  updating_password || new_record?
	end
	
18) flash.discard  --> discards flash upon redirect

19) map.connect '*path', :controller => 'redirect', :action => 'index'  (Should be at the end of routes.rb)
    redirect ctrl
	def index
	  render :text => params.inspect
	end
	
    http://localhost:3000/scis   --->  {"action"=>"index", "controller"=>"redirect", "path"=>["scic"]}
    http://localhost:3000/scis/bar  --->  {"action"=>"index", "controller"=>"redirect", "path"=>["scic","bar"]}
	http://localhost:3000/scis/bar?search=test  --->  {"search"=>"test", "action"=>"index", "controller"=>"redirect", "path"=>["scic","bar"]}
	
	render :text => request.request_uri ---> gives the part after http://localhost:3000
	
20) Naming convention for has_many :through association --> name of the join model
    User , Group ---> Membership
    Person, Company --> Employement	
    Category, Product --> Categorization
	
21) Differentiating between HABTM & has_many :through
    i) do I need to store extra information besides ids of both model
	ii)do I need to treat join as its own model
	
	If ans of anyone is yes the its has_many :through otherwise HABTM.
	
22) Check www.coderpath.com

23) sandbox option for rails console rolebacks changes made to the DB on exit.
    Ex: rails c --sandbox
        rails c production --sandbox

24) Beautifing objects in rails console
    >> project = Project.new  --> inspects object in a single line
	
	>> y project  --> prints the object in yaml format
	   OR
	>> require 'pp'   --> Pretty Printing
       pp project   --> prints object in more readable format
	   
25) Console Tricks -- Railscast 48 (plus some links in show notes section)

26) Alternative ROR API Sites
	* railsapi.org
	* railsbrain.com
	* gotapi.com
	* railsmanual.org
	* noobkit.com
	* ruby.search
	* rorapi.com	   
	
27) zeus gem (Loads server, console and initializes rails env so that everthing runs under 1 sec)

28) http://reverbhq.com/blog/2012/12/ensuring-data-integrity/

29) Product model :-
    belongs_to :category  ---> Association of category with product

	def create_category_from_name
	  create_category(:name => new_category_name) unless new_category_name.blank?
	end
	
	create_category method is by default provided by rails (create_methodname for any association)
	
30) Flash notice :-
    flash[:notice] can aslo be written as
    redirect_to root_url, notice: "Products imported."

31) For generating different color for alternate rows :
    <tr class="<%= cycle :odd, :even %>">
    cycle is a helper method provided by rails.

32) Coverting block to proc :-
    line_items.to_a.sum(&:full_price) === 	line_items.to_a.sum {|l| l.full_price}
	
33) <% @cart.line_items.each do |line_item| %>
      <%= render :partial => 'line_item' %>
	<% end %>  
	
	===
	
	<%= render :partial => 'line_item', :collection => @cart.line_items %>
	
34) logger.debug "Hello world! #{@cart.to_yaml}"   (Railscast 56)
	# debug, info, warn, error, fatal (Severity from low to high)
	
35) By default quries are not shown up in production.log so to see it,
	In environments/production.rb set:
	config.log_level = :debug	(default is :info due to which queries are not shown)
	
36) To display queries in rails console :
    create a .irbrc file in root dir
	~/.irbrc
    --------  
	if ENV.include?('RAILS_ENV') && !Object.const_defined?('RAILS_DEFAULT_LOGGER')
	  require 'logger'
	  RAILS_DEFAULT_LOGGER = Logger.new(STDOUT)
	end

37) Overriding of methods can also be done alias_method_chain  (Screencast - 62)
    Ex: alias_method_chain :valid?(method to over-ride), :without_validation(new method)
	
38) By overriding the below method in  model u can change the id of any object wrt that model. (Screencast - 63) (Check Revised - 63 as well)
	def to_param
		"#{id}-#{permalink}"
	end
	
	Product.find_each :- find_each method fetches the record in batches.
	
	routes.rb
	resources :pages, only: [:index, :new, :create]  --> will generate the routes for only these pages.
	resources :pages, path: "", except: [:index, :new, :create]
	By passing path: "" , it will generate the URL's without the word pages in it.
	Ex localhost:3000/pages/product-categories will become localhost:3000/product-categories
	
39) task :greet do
      p "Hello World"
	end

    task :ask do
	  p "How r u ?"
    end
	
	task :abc => :greet do
	  p 'Task abc called'
	end

    > rake abc
      Calls :greet tak first then calls task :abc 
	  
40) task :winner do
      user = User.find(:first, :order => 'RAND()')
      puts "Winner: #{user.name}"
    end
	rake winner --> Throws error : uninitialized constant User
	
	task :winner => :environment do
      user = User.find(:first, :order => 'RAND()')
      puts "Winner: #{user.name}"
    end
	Loads the rails env first.
	
41)  map.connect 'articles/:year/:month/:day', :controller => 'articles', :month => nil, :day => nil, :requirements => { :year => /\d{4}/ }
     If no action mentioned then ----> default is index action
     Pass optional parameters as nil.
     As the routes are being checked from top to bottom, so to avoid this routes getting executed for some other URL like
     localhost:3000/articles/show/6 ---> we hould specify some requirements as matching condition.

42) <%= link_to_destroy "Destroy", project_path(project), :confirm => 'Are u sure?', :method => :delete %>

43) respond_to do |format|
      format.pdf do
	  end
	end
    ---> throws error (Undefined method pdf for ActionController) because pdf is not one of the default formats in Rails. So we have to register it.

    In any of the config files :-
    Mime::Type.register 'application/pdf', :pdf

44) In ProductsController --> For Basic HTTP Authentication (Railscasts - 82) (Pop up box promting for username/password)

	before_filter :authenticate

	protected

	def authenticate
	  authenticate_or_request_with_http_basic do |username, password|
		username == "foo" && password == "bar"
	  end
	end
	
45) YAML.load_file("#{RAILS_ROOT}/config/config.yml") ---> returns a hash

46) Customized method to print the values of variable in log

    logger.debug_variables(binding)

    initializer/logger_addition.rb
    logger = ActiveRecord::Base.logger
	def logger.debug_variables(bind)
	  vars = eval('local_variables + instance_variables', bind)
	  vars.each do |var|
		debug  "#{var} = #{eval(var, bind).inspect}"
	  end
	end
	
47) Routes by default also generates formatted rotes means routes for different formats (ex : html, rss etc)
    check rake routes
	
48) To execute any kind of format(extns like pdf, rss, xml etc) for any given action, write the below line in routes.rb
    map.connect ':controller/:action.:format'

49) RESTful == Hypermedia APIs

50) Caching is by default off in development environment & ON on production env.
    config.action_controller.perform_caching = false ---> devleopment
	
51) If u add any new folders(for ex: services) in app directory then, u have to mention it in the environment.rb file like this
    config/environment.rb  (or any initializer file)
	config.load_paths << "#{RAILS_ROOT}/app/services"
	
52) See caching in rails (types of caching in rails). One is page caching
    We can also expire cache based on a given condition. (Railscast - 89)(Also has a revised episode)
	
53) One more type of caching in fragment caching in which we cache only a portion of the page instead of the whole page(Page Caching).
    Railscast - 90 (Also has a revised episode)
	
54) Third type of caching is Action Caching.
    Suppose there is a before filter like :
    before_filter :authorize #---> Method for checking authorization
	then if page caching is enabled and once the page is cached then this before_filter will be bypassed
    whereas in case of action caching it will not be bypassed means it will executed for every single action.

54.1) Fragment Caching can improved by using touch (Railscasts : 172)

	comment.rb
	belongs_to :article, :touch => true

	articles/show.html.erb
	<% cache @article do %>
	  ...
	<% end %>

	So, here if we only caching articles and not their comments(using :touch => true through the assciation) then comments will not get reflected and cached page for the article will appear.
	So, by passing :touch => true through assciation, whenever a comment object is created or altered it touches the article object thereby changing articles timestamp, so the cache for @article auto-expires
	
	<% cache @article do %> means <% cache @article.cache_key do %>
	
	article = Article.first
	article.cache_key ===> articles/1-20090606223425
	article.touch   # this will change the updated_at column for article with current timestamp.
	article.updated_at or article.cache_key ===> articles/1-20090606223450
	
55) content_for :-
	You can use the content_for method in your template to store up the content of the block inside the variable :side, so that it can be used later on in the layout.
	<% content_for :side do %>
	  ...
	<% end %>

	application.html.erb :-
	<div id="side">
	  <%= yield(:side) || render(:partial => '...' %>
	</div>

56) Debugging Variables in Views
	<%= debug @products %>
	<%= debug params %>
	<%= debug request.env %>

57) reverse_merge! method is used to not to merge any existing params in the given hash.

58) rake -T time --> list all tasks related to Timezone
	rake time:zones:all  --> list all time zones which can be set in config/application.rb
    rake time:zones:local  --> Displays local time zone by checking system time.
	rake time:zones:us
	
	In config/environment.rb
	config.time_zone = "Pacific Time (US & Canada)"  -->(i.e; the output of rake time:zones:local)
	
	Rails saves the time as UTC in DB and while displaying it coverts to mentioned time zone.
	
	In rails console :-
	>> Product.first.released_at ---> Displays time by translating UTC into Pacific time zone
	>> Product.first.released_at_before_type_cast ---> Displays UTC
	
	Watch Revised Episode 106 for more details
	
59) Detecting change in attribute :-
    --------------------------------
    p = Product.first
	p.name = 'book'
    p.changed? => false
    p.name = 'pen'
    p.changed? => true
    p.name_changed? => true	(<attribute-name>_changed? method)
	
	p.name_was => 'book'
	p.name_change => ['book', 'pen']  (old_name, new_name)
	p.changed => ['name'] (Array of attributes that were changed)
	
	p.changes => {'name' => ['book', 'pen']}
	
	But this change method will only work it the attribute value is being changed with setter method.
	so if u do
	p.name.upcase! => 'PEN'
	p.changed => false
	p.save => no update query will be fired
	
	But the above problem can be resolved if u call a method named (<attribute-name>_will_change!)
	p.name_will_change! => returns old name
	p.name.upcase! => 'PEN'
	p.changed => true
	and all the other change methods will also function properly.

59) scopes are useful because they can be used for chaining. (means we can chain one scope after the other).
	
	class Product < ActiveRecord::Base
	  belongs_to :category
	  scope :cheap, :conditions => { :price => 0..5 }
	  scope :recent, lambda { |*args| {:conditions => ["released_at > ?", (args.first || 2.weeks.ago)]} }
	  scope :visible, :include => :category, :conditions => { 'categories.hidden' => false }
	end

    we can do chaining like 
	Product.recent.cheap
	
	Also, lambda is useful because it becomes active only when it get called. For ex: say our sever has been started a month back then 2.weeks.ago would become (1 month + 2 weeks) ago if we are not using lambda.
	Lambda can be written to accept an argument or without any arguments as well.
	scope :recent, lambda { {:conditions => ["released_at > ?", 2.weeks.ago]} }
	
	We can also use these scopes of Product model with their association.
	Ex: Category.first.products.cheap.recent
	
	We can also use association with a scope.
	For ex:- scope :visible, :include => :category, :conditions => { 'categories.hidden' => false }
	Product.visible will only output the products which have categories which are not hidden.
	
	We can also do Product.visible.cheap.recent (scope chaining)
	
	We can also append ActiveRecord queries after the scopes like
	Product.recent.cheap.where("name like 'a%'")
	Product.recent.cheap.all(:order => 'released_at')
	
60) check : rake -T gems
    rake gems:unpack --> unpacks the gem inside vendor directory
	rake gems:build  --> generates the code for native gems
	
61) caching through an instance variable :-
    def products
	  @products ||= Product.find(:all, :conditions => conditions)
	end
	The above will fire the query only once & return the cached instance variable for every other request.
	
62) Get browser details of a user by using the gem : browser_details
    https://github.com/gshutler/browser_details

63) Anonymous scope :-
    ------------------
	def find_products
      scope = Product.scoped({})
	  scope = scope.scoped(:conditions => ["products.name LIKE ?", "%#{keywords}%"]) unless keywords.blank?
	  scope = scope.scoped(:conditions => ["products.price >= ?", minimum_price]) unless minimum_price.blank?
	  scope
	end

64) Rails.cache ---> added in Rails 2.1 which is a much lower level cache and can be used to cache anything not only view layers. 
	(Railscast - 115)
	Rails.cache.write('date', Date.today)  --> Writes data onto the cache
	Rails.cache.read('date')               --> Reads data from the cache
	Rails.cache.fetch('time') { Time.now } --> Writes for the first time then reads on subsequent request
	Ex :- To cache all the categories
	def self.all_cached
	  Rails.cache.fetch('Category.all') { all }
	end
	
	Can also fetch newly created categories, by destroying the cache on callback & creating again.

	Rails.cache.read('date')			   --> Destroys data from the cache
	
65) Rails.cache is a normal hash
    But for 3 differnt servers it will create a problem(cache gets created on only 1 server)
	So, a better way to store is to set up mem cache server(mem_cache_store) , point the app to that server to get cache
	
	cache = ActiveSupport::Cache.lookup_store(:mem_cache_store)
	cache.fetch('time') { Time.now }
	
	We can also set expiry time on the cache if we are using mem_cache ,so that it destroyed in 5 secs & gets newly created since we are using fetch method.
	
	cache.fetch('time', :expires_in => 5) { Time.now }

66) simple_format is a helper method that recognizes line breaks within the text. (Railscast - 117)
	<%= simple_format(h(@page.content))%>
	
	Similar to simple_format there is one more helper method : textilize (Ex : <%= textilize @page.content %>)
	
	There is another gem RedCloth(Version 3.3) which can be used for test styling instead of the helper method : simple_format
	
67) Raising an error explicitly.

	def show
	  if params[:permalink]
		@page = Page.find_by_permalink(params[:permalink])
		raise ActiveRecord::RecordNotFound, "Page not found" if @page.nil?    #----> Throwing an exception explicitly
	  else
		@page = Page.find(params[:id])
	  end
	end

	routes.rb
	map.static ':permalink', :controller => 'pages', :action => 'show'
	---> matches http://localhost:3000/about
	
68) Liquid is a templating languague which is used to bind dynamic content inside static pages. (Railscast - 118)

69) We can access RDoc in our local system by using command	
    > gem server
	Then RDoc gets rendered in port 8808 and can accessed using the link :- http://localhost:8808
	
70) populator gem is used to populate the database with large number of records with random data.
    This gem cannot be used to generate email_ids or phone nos or postal code etc, so there is another gem for that known as faker.
	
71) <%= request.subdomains.inspect %>
    Gives an array of subdomains from the request object.
	Check the subdomain-fu gem for using subdomain in ur rails website.
	
72) Creating association for same model but with a different name to tell different relationship
    
	invitation.rb model :-
	belongs_to :sender, :class_name => 'User'
	has_one :recipient, :class_name => 'User'
	
73) Seeting layout inside a method :
    self.class.layout(@current_blog.layout_name || 'application') --> For Blog object having layout_name as a column in blogs table
	
74) To find Rails environment for inside of a Rails app
    env = Rails.env

75) system method is used to execute system commands for inside of a Rails app
    system "/usr/bin/rake #{task} #{args.join(' ')} --trace >> #{Rails.root}/log/rake.log &"	
	
	& at the end is used to run the rake task in background
	>> is used to put the log in a seperate log file.
	
76) MemCache class can be used for client server communication. (Railscast - 128)

77) You can also go back from a action by using :- redirect_to :back
    Ex:
	def create
      current_cart.cart_items.create!(params[:cart_item])
	  flash[:notice] = "Product added to cart"
	  redirect_to :back
	end
	
    the value stored in :back is actually request.env['HTTP_REFERER'] which is sent by the browser.
	Ex : Good Example of Shopping Cart (Railscast - 131)
	cart_items_controller.rb
	def create
	  current_cart.cart_items.create!(params[:cart_item])
	  flash[:notice] = "Product added to cart"
	  session[:last_product_page] = request.env['HTTP_REFERER'] || products_url
	  redirect_to current_cart_url
	end
	
	carts/show.html.erb
	<% if session[:last_product_page] %>
	  <%= link_to "Continue Shopping", session[:last_product_page] %> |
	<% end %>

78) To load all the rake file in one line :
	Dir["#{File.dirname(__FILE__)}/tasks/*.rake"].sort.each { |ext| load ext }
	
79) To vendorize a gem u need to use the below command from vendor/gems dir
    app/vendor/gems> gem unpack gem_name_version
	
80) flash.delete(:notice) means flash the notice then delete the flash message, so that it doesnot get carried over to the next request.

81) respond_to do |format|
      format.html { redirect_to @review.product }   ---> renders show.html.erb
      format.js									    ---> 		 show.js.erb
	  format.pdf									--->		 show.pdf.erb
	  ..etc
	end
	
82) To create a function for a jQuery element use jQuery.fn.<function_name>
	jQuery.fn.submitWithAjax = function() {
	  this.submit(function() {
		$.post(this.action, $(this).serialize(), null, "script");
		return false;
	  })
	  return this;
	};

	$(document).ready(function() {
	  $("#new_review").submitWithAjax();
	})
	
83) To reset a form in jQuey, u can reset method.
    $("#new_review")[0].reset();  --> [0] since $("#new_review") returns an array of jQuery Element.

84) Memoization :- (Railscast - 137, Revised episode available)
    --------------
    Its an alternative to caching instance varible.
    old :- @file_size ||= calculate_filesize
    new :- 
	
	class Product < ActiveRecord::Base
	  extend ActiveSupport::Memoizable
	  
	  belongs_to :category
	  
	  def filesize(num = 1)
		# some expensive operation
		sleep 2
		12345789 * num
	  end
	  memoize :filesize
	end

	Memoization is deprecated from Rails 3.2.8 so u can use memoist gem for this as an alternative
         OR	
	class Product < ActiveRecord::Base
	  def filesize(*args)
		@filesize ||= {}
		@filesize[args] ||= calculate_filesize(*args)
	  end

	private
	  def calculate_filesize(num = 1)
		sleep 0.5
		4815162342 * num
	  end
	end
	
85) t method means translate method of I18n is available only on controllers & views , to access the same at other places use
    I18n.translate  --> Railscast - 138

86) There are few ways to create nested routes :-  (Article --> has_many Comments)
    1) map.resources :articles do |article|
		article.resources :comments
	   end
	
	2) map.resources :articles, :has_many => :comments  (Make sure use correct routing paths in views)  --> Railscast 139
	
	3) map.resources :articles, :has_many => :comments, :shallow => true
	
87) application_helper.rb
	def admin_area(&block)
	  if admin?
		concat content_tag(:div, capture(&block), :class => 'admin')
	  end
	end

	rhtml
	<% admin_area do %>
	  <%= link_to "Edit", edit_product_path(@product) %> |
	  <%= link_to "Destroy", @product, :confirm => 'Are you sure?', :method => :delete %>
	<% end %>

88) Product.find_by_price(3) # => nil

	Product.find_by_price!(3) # => Raises RecordNotFound Exception
	
	Product.find_last_by_price(4.99) => Finds last record directly (instead of fetching all records and then displaying the last one)
	
	Product.all(:joins => :category, :conditions => { :categories => { :name => 'Clothing' } })	=> We can give the join condition in terms of Hash as well.

89) PayPal for Developers for Testing purpose :- http://developer.paypal.com

90) To render nothing write :
    render :nothing => true
	
91) serialize :params
    This will convert the params hash into YAML format and saves it to DB & while retrieving it converts back to hash(means original format), means o/p will always be in the form of i/p.

92) Payment Gateway sites :-
    Paypal
    authorize.net
	
93) after_initialize method is used in config files to run something after initialization. 
	Ex : Initializing payment gateway using active merchant
	config.after_initialize do
	  ActiveMerchant::Billing::Base.mode = :test
	  ::GATEWAY = ActiveMerchant::Billing::PaypalGateway.new(
		:login => "seller_1229899173_biz_api1.railscasts.com",
		:password => "FXWU58S7KXFC6HBE",
		:signature => "AGjv6SW.mTiKxtkm6L9DcSUCUgePAUDQ3L-kTdszkPG8mRfjaRZDYtSu"
	  )
	end

94) ::GATEWAY --> :: is used to prepend before a constant so that it can be accessed from applications root, otherwise it will be accessible from from the scope of current class.

95) gem install ---
    Install the gem on your system(can also run some malacious code on ur system or servers)
	
	so to cross check do
	gem fetch <gem_name> then
	gem unpack <gem_name>
	
96) rails store -m <template_name> (Railscast 148) See the links in show notes section (Refer : http://m.onkey.org/rails-templates)
	rails store -m base_template.rb :- This base_template will contain the commands that we want to run after the new rails project store is created.
	
	base_template.rb :-

	run "echo TODO > README"

	gem 'RedCloth', :lib => 'redcloth'
	gem 'mislav-will_paginate', :lib => 'will_paginate', :source => 'http://gems.github.com'
	rake "gems:install"

	if yes?("Do you want to use RSpec?")
	  plugin "rspec", :git => "git://github.com/dchelimsky/rspec.git"
	  plugin "rspec-rails", :git => "git://github.com/dchelimsky/rspec-rails.git"
	  generate :rspec
	end

	git :init

	file ".gitignore", <<-END
	.DS_Store
	log/*.log
	tmp/**/*
	config/database.yml
	db/*.sqlite3
	END

	run "touch tmp/.gitignore log/.gitignore vendor/.gitignore"
	run "cp config/database.yml config/example_database.yml"

	git :add => ".", :commit => "-m 'initial commit'"
	
100)ab command (Appache Benchmark) is used for benchmarking (comparing). Server should be run in production mode while benchmarking.
    > script/server -e production -d (-d option is used to detach this process)
	> ab -n 100 http://127.0.0.1:3000/processes/list
	> ab -n 100 http://127.0.0.1:3000/processes_list

101) Rails 2.3 extras :-
	# find in batches
	Product.count
	Product.find_in_batches(:batch_size => 10) do |batch|    ---> batch => array of 100 objects
	  puts "Products in batch: #{batch.size}"
	end
	Product.each(:batch_size => 10) do |product|             ---> passing single product at a time while loading 10 products at 1 go 
	  puts product.name
	end

	# scoped_by (Dynamic scopes --> scoped_by_<attr-name>)
	Product.scoped_by_price(4.99).size     --> Till Product.scoped_by_price(4.99) query is not fired, its fired on .size or .first etc
	Product.scoped_by_price(4.99).first
	Product.scoped_by_price(4.99).scoped_by_category_id(3).first   --> chaining of these dynamic scopes can also be done

	# try method  (Returns product's name if there's product with price 4.99 otherwise nil instead of NoMethodError)
	Product.find_by_price(4.99).try(:name)
	
	product.rb --> Default scope gets applied on every query
	default_scope :order => "name"

	categories_controller.rb
	render 'new' --> action_name
	render 'products/edit' --> controller/action_name

	products/index.html.erb
	<%= render @products %>  (Render partial products with collection of products)

	products/show.html.erb
	<%= render @product %>  (Render partial product for a single products)

	Checkout release notes for more : http://guides.rubyonrails.org/2_3_release_notes.html
	
102) If u r writing (redirect_to :id => nil) on a create action like
	
	def create
	  @commentable = find_commentable
	  @comment = @commentable.comments.build(params[:comment])
	  if @comment.save
		flash[:notice] = "Successfully created comment."
		redirect_to :id => nil   ---> will redirect you to the index action of the respective commentable type (Article or photo or event)
	  else
		render :action => 'new'
	  end
	end
	
103) To get class methods get included when we include a module, add a module named ClassMethods inside that module and place all the methods inside ClassMethods module and add a small hook to get it included means include the methods inside ClassMethods when ever the parent module gets included.
	module ControllerMacros
	  def self.included(base)
		base.extend(ClassMethods)
	  end
	  
	  module ClassMethods
		def it_should_require_admin_for_actions(*actions)
		  actions.each do |action|
			it "#{action} action should require admin" do
			  get action, :id => 1
			  response.should redirect_to(login_url)
			  flash[:error].should == "Unauthorized Access"
			end
		  end
		end
	  end
	end
	
104) Grouping gems for two environments
	 gem 'debugger', group: [:development, :test]
	 
105) logger.debug { "Article Count: #{Article.count}" } 
     Putting {} braces besides logger.debug will only excute the code inside {} when the logger is in debug mode.
 	 
	config/environments/development.rb (log_tags appends the mentioned stuffs into the beginning of the log message)
	config.log_tags = [:uuid, :remote_ip, lambda { |req| Time.now }] --> (unique user id, User IP Addr, Time)

	config/initializers/log_formatter.rb (Over-riding the below Logger class will allow you to modify the log messages)
	class Logger::SimpleFormatter
	  def call(severity, time, progname, msg)
		"[#{severity}] #{msg}\n"
	  end
	end

106) date.to_time   -------> 2012-04-08 00:00:00 +0530
	 But while making queries rails will convert time it to UTC time --> 2012-04-08 05:30:00
	 date.to_time_in_current_zone ---->Prints the Time in UTC -> Sun, 08 Apr 2012 00:00:00 UTC +00:
	 So, always check the time that's in the query.
	 
107) Always set whitlisting to true	
	 config/application.rb
	 config.active_record.whitelist_attributes = true
     so that nobody is able to access any protected attributes like is_admin through mass assignment.
	 Use attr_accessible in all the models for the attributes that a user can modify. (attr_protected --> attributes that a user cannnot access.)
	 
108) To access routes in rails console use 
     > app.products_path   --> "/products"
     > app.get _   or app.get "/products"   --> select * from products --> 200 (Success Code)
     > app.class  --> ActionDispatch::Integration::Session
     > app.cookies --> gives u what cookies were set
     > app.response.headers	--> Gives response header
     > app.response.body --> Response body
     > app.assigns(:products).size --> Gives u the instance variable which was set on the last request

109) By default the rails console prints the sql query which is being fired in the console like
     Product.count ---> Select count(*) from products
     To off it just set ActiveRecord::Base.logger.level to anything greater than 0.
     Ex : ActiveRecord::Base.logger.level = 1

110) To set the default behaviour of rails console create a file at ~ named .irbrc, this file will be loaded whenver a rails console is loaded
	 This is for apps having rails < Rails 3.2
    > touch ~/.irbrc
	
	#!/usr/bin/env ruby
	require 'irb/completion'   # tab completion in irb
	require 'irb/ext/save-history' # To enable saving history of previous commands

	IRB.conf[:PROMPT_MODE] = :SIMPLE
	IRB.conf[:SAVE_HISTORY] = 1000  # 1000 previous commands
	IRB.conf[:HISTORY_FILE] = "#{ENV['HOME']}/.irb_history"

	# ActiveRecord::Base.logger.level = 1 if defined? ActiveRecord::Base   # To restrict sql query logging

	# Prints the object in yaml format
	def y(obj)
	  puts obj.to_yaml
	end

	# open the called in textmate
	class Object
	  def mate(method_name)
		file, line = method(method_name).source_location
		`mate '#{file}' -l #{line}`
	  end
	end

	Install the hirb gem to see the output of queries in nice table format
	gem install hirb 
	Add the below code in .irbrc file to make use it in every project's rails console (Otherwise can also add this gem to ur gemfile to access this gem in every environment)
	
	# Break out of the Bundler jail
	# from https://github.com/ConradIrwin/pry-debundle/blob/master/lib/pry-debundle.rb
	if defined? Bundler
	  Gem.post_reset_hooks.reject! { |hook| hook.source_location.first =~ %r{/bundler/} }
	  Gem::Specification.reset
	  load 'rubygems/custom_require.rb'
	end

	if defined? Rails
	  begin
		require 'hirb'
		Hirb.enable
	  rescue LoadError
	  end
	end
	
	Ex :-
	require 'hirb'
	Hirb.enable
	Product.limit(5)
	
	Rails 3.2 onwards :- (Revised :- 148)
	--------------------
	In Rails 3.2 create a .railsrc file in ~ and place all the options which u want to apply every time u create a new rails app. 
	> echo -d mysql --skip-test-unit --skip-sprockets > ~/.railsrc
	
	To see all the available options
	> rails new --help
	
	We can also tell what app template to refer after creating a rails project means whats commands to be fired every time a new rails app 
	is created using -m option
	> rails new abc -m app_template.rb
		
	app_template.rb (This is based on Thor gem and its documentation is at : http://guides.rubyonrails.org/generators.html#generator-methods)
	----------------
	remove_file "README.rdoc"
	create_file "README.md", "TODO"

	gem "rspec-rails", group: [:test, :development]
	run "bundle install"
	generate "rspec:install"

	if yes? "Do you want to generate a root controller?"
	  name = ask("What should it be called?").underscore
	  generate :controller, "#{name} index"
	  route "root to: '#{name}\#index'"
	  remove_file "public/index.html"
	end

	git :init
	append_file ".gitignore", "config/database.yml"
	run "cp config/database.yml config/example_database.yml"
	git add: ".", commit: "-m 'initial commit'"

	---------------------------------------------------------------------------------------------------------------------------------------
	We can also use app builders using -b option to generate app builders which can override default methods of rails app creation
	> rails new abc -b app_builder.rb
	
	app_builder.rb
	--------------
	class AppBuilder < Rails::AppBuilder
	  def readme  # Overridden method readme
		create_file "README.md", "TODO"
	  end
	  
	  def test # Overridden method readme
		@generator.gem 'rspec-rails', group: [:test, :development]
		run 'bundle install'
		generate 'rspec:install'
	  end
	  
	  def leftovers
		if yes? "Do you want to generate a root controller?"
		  name = ask("What should it be called?").underscore
		  generate :controller, "#{name} index"
		  route "root to: '#{name}\#index'"
		  remove_file "public/index.html"
		end

		git :init
		append_file ".gitignore", "config/database.yml"
		run "cp config/database.yml config/example_database.yml"
		git add: ".", commit: "-m 'initial commit'"
	  end
	end

	To check the list of methods that we can override , check the file :
	https://github.com/rails/rails/blob/master/railties/lib/rails/generators/rails/app/app_generator.rb

	To do all these we can also use 
	http://railswizard.org --> Not maintained nowadys
	http://appscrolls.org/ --> Very good (http://drnicwilliams.com/2012/04/10/instant-new-rails-applications-with-the-app-scrolls/)
	> gem install appscrolls
	> scrolls list --> gives u the list of different scolls available
	> scrolls new app_name -s rspec capybara guard
	
111) gem install awesome_print  --> Prints the object in nice & organized way
	 > require 'awesome_print'
	 > ap Product.first.attributes

112) gem install methodfinder
     > require 'methodfinder'     --> Print all the method names that can give the desired output
	 > "abc".find_method("ABC")   --> ["String#swapcase", "String#swapcase!", "String#upcase", "String#upcase!"]

113) Checkout irbtools gem which contains all the gems like awesome_print , methodfinder etc
     https://github.com/janlelis/irbtools
	 
114) To run commands with sudo permission on a server use
	 default_run_options[:pty] = true  --> this will ask u for password in the shell

	 task :hello do
	  run "#{sudo} cp ~/hello /hello"
	 end
     
115) Time.parse(@released_at_text) --> will give u the DateTime object (@released_at_text = '2012-11-17 11:17:00')
     Time.zone.parse(@released_at_text) --> will give u the DateTime object in the current time zone
	 Use chronic gem to input date in various string formats like Tomorrow at 20:00 etc
	 
116) Values of virtual attributes can be persisted and displayed in the form using attr_writer 
     attr_writer :released_at_text, :tag_names
	 validate :check_released_at_text  
	 before_save :save_released_at_text
   	 
	 def save_released_at_text
		self.released_at = Time.zone.parse(@released_at_text) if @released_at_text.present?
	 end

	 def check_released_at_text
		if @released_at_text.present? && Time.zone.parse(@released_at_text).nil?
			errors.add :released_at_text, "cannot be parsed"
		end
	 rescue ArgumentError
		errors.add :released_at_text, "is out of range"
	 end
	 
117) > export RAILS_ENV=staging
     > rails c --> starts the rails console or whatever u want in staging env.
	 
118) Gems can be grouped  and given whatever name u want(for example checks assets group in gemfile & how its included in application.rb file)
	For Ex : 
	Gemfile
	group :profiling do
	  gem 'ruby-prof'
	end

	config/application.rb
	Bundler.require(*Rails.groups(:assets => %w(development test), :profiling => %w[staging development])

119) Sending e-mail in a Rails App

	terminal : rails g mailer user_mailer signup_confirmation

	app/mailers/user_mailer.rb
	class UserMailer < ActionMailer::Base
	  default from: "railscasts@example.com"

	  def signup_confirmation(user)
		@user = user
		mail to: user.email, subject: "Sign Up Confirmation"
	  end
	end

	app/views/user_mailer/signup_confirmation.text.erb
	<%= @user.name %>,
	Thank you for signing up.
	<%= user_url(@user) %>

	Note: In the episode I just passed the @user model in directly in the HTML template (below) but that generates a relative URL. You need to use the url helper method to generate a full URL.

	app/views/user_mailer/signup_confirmation.html.erb
	<p><%= @user.name %>,</p>
	<p>Thank you for signing up.</p>
	<p><%= link_to "User Profile", user_url(@user) %></p>

	users_controller.rb
	UserMailer.signup_confirmation(@user).deliver

	config/development.rb
	# Don't care if the mailer can't send
	config.action_mailer.raise_delivery_errors = true

	# Change mail delvery to either :smtp, :sendmail, :file, :test
	config.action_mailer.delivery_method = :smtp
	config.action_mailer.smtp_settings = {
	  address: "smtp.gmail.com",
	  port: 587,
	  domain: "railscasts.com",
	  authentication: "plain",
	  enable_starttls_auto: true,
	  user_name: ENV["GMAIL_USERNAME"],
	  password: ENV["GMAIL_PASSWORD"]
	}

	# Specify what domain to use for mailer URLs
	config.action_mailer.default_url_options = {host: "localhost:3000"}

120) Storing private info in YAML file (Can also check Figaro gem)
	
	terminal
	echo /config/application.yml >> .gitignore
	cp config/application.yml config/application.example.yml

	articles_controller.rb
	http_basic_authenticate_with name: CONFIG[:username], password: CONFIG[:password]

	config/initializers/secret_token.rb
	Blog::Application.config.secret_token = CONFIG[:secret_token]

	config/application.yml
	username: "admin"
	password: "secret"
	secret_token: "024e1460..."
	development:
	  host: "localhost:3000"
	test:
	  host: "test.local"
	production:
	  host: "blog.example.com"

	config/application.rb (Should be written in between bundler def and class def)
	CONFIG = YAML.load(File.read(File.expand_path('../application.yml', __FILE__)))
	CONFIG.merge! CONFIG.fetch(Rails.env, {})
	CONFIG.symbolize_keys!

	# config/application.rb
	config.action_mailer.default_url_options = {host: CONFIG[:host]}

	ENV Alternative
	config/application.rb
	config = YAML.load(File.read(File.expand_path('../application.yml', __FILE__)))
	config.merge! config.fetch(Rails.env, {})
	config.each do |key, value|
	  ENV[key] = value unless value.kind_of? Hash
	end

121) Alternative solution to optimistic locking (Revised Episode :- 59)
	Alternative solution using updated_at
	products/_form.html.erb
	<%= f.hidden_field :original_updated_at %>

	product.rb
	attr_accessible :original_updated_at # ...
	validate :handle_conflict, only: :update

	def original_updated_at
	  @original_updated_at || updated_at.to_f
	end
	attr_writer :original_updated_at

	def handle_conflict
	  if @conflict || updated_at.to_f > original_updated_at.to_f
		@conflict = true
		@original_updated_at = nil
		errors.add :base, "This record changed while you were editing. Take these changes into account and submit it again."
		changes.each do |attribute, values|
		  errors.add attribute, "was #{values.first}"
		end
	  end
	end

122) Use letter_opener gem in development env to open the exception notifications in a browser window (Revised :- 104)
	gem 'letter_opener', group: :development   # Gemfile
	config.action_mailer.delivery_method = :letter_opener   # config/development.rb
	
123) Migration for a polymorphic association  (Checkout Revised : 154 for more polymorphic association tips)
     class CreateComments < ActiveRecord::Migration
       def change
		 create_table :comments do |t|
		   t.text :content
		   t.belongs_to :commentable, polymorphic: true
		   
		   t.timestamps
		 end
		 add_index :comments, ["commentable_id, :commentable_type]
	   end
	 end

124) To escape(execute) erb-html code inside javascript, we have to use the j method (use remote: true to make a ajax request) (Revised-136)
	 <%= link_to "New Task", new_task_path, id: "new_link", remote: true %>
	 new.js.erb :-
     Ex: $('#new_link').hide().after('<%= j render("form") %>')
	 
	 We can also use escape_javascript method :
	 Ex: products/index.js.erb
	     $("#products").html("<%= escape_javascript(render("products")) %>");


	 
125) Use link_to_unless_current helper method so to switch between hyperlink & text for a given link. (Revised - 138) 	
	layouts/application.html.erb
	Language:
	<%= link_to_unless_current "English", locale: "en" %> |
	<%= link_to_unless_current "Wookieespeak", locale: "wk" %>

126)For translation, if the keys are unique can we can directly use the keys to display their values. 
	config/locals/en.yml
	en:
	  products:
		index:
		  title: "Browse Products"
		  description: "Thank you for visiting our store. Now take out your wallet and buy something."

	<h1><%= t ".title" %></h1> instead of <h1><%= t "products.index.title" %></h1>
	
127) Different ways to set locale for a user
	def set_locale
	  I18n.locale = params[:locale] if params[:locale].present?
	  # current_user.locale
	  # request.subdomain
	  # request.env["HTTP_ACCEPT_LANGUAGE"]  -- sent through user's browser
	  # request.remote_ip  -- find locale using geolocation with IP
	end	
	
128) Use 'Globalize 3' gem translate say product name which is stored in the database
	 Check guides page on Internationalization
	 
129) We can set categories for a product using category ids as well
	p = Product.first
	p.category_ids # []
	p.category_ids = [1, 2]  # Insert 2 records
	p.categories	# Returns array of two categories
	
130) To assign a unique id to a set of checkboxes(say categories belonging to a product), use the helper method dom_id
	
	products/_form.html.erb
	<%= hidden_field_tag "product[category_ids][]", nil %>   // Set to nil so that if no checkboxes are selected then nil is submitted
	<% Category.all.each do |category| %>
	  <%= check_box_tag "product[category_ids][]", category.id, @product.category_ids.include?(category.id), id: dom_id(category) %>
	  <%= label_tag dom_id(category), category.name %><br>  //Labels added along with dom_id for the category so that clicking on name checks the checkbox
	<% end %>
	
	simple_form, formtastic are the two gems which provide many more methods to build a form easily.
	
131) For populating states of a country
	people/new.html.erb
	<%= f.grouped_collection_select :state_id, Country.order(:name), :states, :name, :id, :name, include_blank: true %>

	app/assets/javascripts/people.js.coffee
	jQuery ->
	  $('#person_state_id').parent().hide()
	  states = $('#person_state_id').html()
	  $('#person_country_id').change ->
		country = $('#person_country_id :selected').text()
		escaped_country = country.replace(/([ #;&,.+*~\':"!^$[\]()=>|\/@])/g, '\\$1')
		options = $(states).filter("optgroup[label='#{escaped_country}']").html()
		if options
		  $('#person_state_id').html(options)
		  $('#person_state_id').parent().show()
		else
		  $('#person_state_id').empty()
		  $('#person_state_id').parent().hide()

132)There is no need to give format in the respond_to block like
	respond_to do |format|
	  format.html 
	  format.atom
	end
	Mention the format directly in the link
	<%= link_to image_tag("feed-icon-28x28.png"), articles_url(format: "atom") %>

133) Since jQuery comes by default with Rails 3, so to use any jQuery pluggin like accordion or autocomplete just include jquery-ui JS.

	app/assets/javascripts/application.js
	//= require jquery
	//= require jquery-ui
    //= require jquery_ujs
	//= require_tree .

134) From Rails 3.1, there is a new attribute named data which can be very useful. (Revised - 102)

	products/_form.html.erb
	<%= f.text_field :category_name, data: {autocomplete_source: Category.order(:name).map(&:name)} %>
	
	Further this data attribute can used for autocompletion
	
	app/assets/javascripts/products.js.coffee
	jQuery ->
	  $('#product_category_name').autocomplete
		source: $('#product_category_name').data('autocomplete-source')

135) To chain a search query :

	models/search.rb
	def products
	  @products ||= find_products
	end

	private
	def find_products
	  products = Product.order(:name)
	  products = products.where("name like ?", "%#{keywords}%") if keywords.present?
	  products = products.where(category_id: category_id) if category_id.present?
	  products = products.where("price >= ?", min_price) if min_price.present?
	  products = products.where("price <= ?", max_price) if max_price.present?
	  products
	end

136) While using Thinking Sphinx as a search engine for ur rails app, to solve the problem of re-indexing for every new record created, check the Delta Indexes section of Thinking Sphinx.

137) Defining associations with Factory Girl.
     Say, there is a class User and a class Article and Article belongs_to User
	 
	Factory.define :user do |f|
	  f.sequence(:username) { |n| "foo#{n}" }
	  f.password "foobar"
	  f.password_confirmation { |u| u.password }
	  f.sequence(:email) { |n| "foo#{n}@example.com" }
	end

	Factory.define :article do |f|
	  f.name "Foo"
	  f.association :user  # or f.association :author, :factory => :user # if the association name is author instead of user
	end
	
	spec/factories.rb  (From Revised Episode)
	FactoryGirl.define do
	  factory :user do
		sequence(:username) { |n| "foo#{n}" }
		password "foobar"
		email { "#{username}@example.com" }
		admin false
		
		factory :admin do
		  admin true
		end
	  end
	  
	  factory :article do
		name "Foo"
		user
	  end
	end

138) user = Factory(:user, :username => 'frank', :password => 'secret') # creates a record in test database
     is same as 
	 user = Factory.create(:user, :username => 'frank', :password => 'secret')
	 
	 user = Factory.build(:user, :username => 'frank', :password => 'secret') # creates a object in memory
	 
	Alternatives of Factory Girl are Machinist, Object Daddy	

139) We need not pass the id for the resource when its the current one :- (Railscast :- 160)

	layouts/application.html.erb
	<div id="user_nav">
	  <% if current_user %>
		<%= link_to "Edit Profile", edit_user_path(:current) %> |
		<%= link_to "Logout", logout_path %>
	  <% else %>
		<%= link_to "Register", new_user_path %> |
		<%= link_to "Login", login_path %>
	  <% end %>
	</div>

140) Profiling tools for performance optimization :- (Railscast :- 161)
     1. New Relic RPM Developer Mode
	 2. FiveRuns TuneUp
	 3. Rack::Bug
	 
141) Using includes & joins
	@products = Product.order("categories.name").joins(:category).select("products.*, categories.name as category_name")
    # or Product.order("name").includes(:category)
	
142) Creating index for a column while creating a migration 
     rails g scaffold page name content:text ancestry:string:index
	 
143) Inverse relationship :-
     
	models/friendship.rb
	--------------------
	belongs_to :user
	belongs_to :friend, :class_name => "User"

	models/user.rb
	--------------
	has_many :friendships
	has_many :friends, :through => :friendships
	has_many :inverse_friendships, :class_name => "Friendship", :foreign_key => "friend_id"
	has_many :inverse_friends, :through => :inverse_friendships, :source => :user

144) To update multiple records in which array of product_ids comes from params and rest of the attributes, either some value or blank
    
    def update_multiple
	  @products = Product.find(params[:product_ids])
	  @products.each do |product|
		product.update_attributes!(params[:product].reject { |k,v| v.blank? })  # Reject nil means not modified
	  end
	  flash[:notice] = "Updated products!"
	  redirect_to products_path
	end
	
145) fields_for :-
     -------------
	 fields_for is a helper method which is used inside a form_tag to create a form either for a single or multiple model objects and acess the form builder methods.
	 
146) There is a class method update for a model with the help of which we can update multiple records
     @products = Product.update(params[:products].keys, params[:products].values)

	 But this update method igonres validation errors.
	 But the above query returns all the sucessfully updated objects. So, it can be done by the below code (Railscast - 198)
	 
	def update_individual
	  @products = Product.update(params[:products].keys, params[:products].values).reject { |p| p.errors.empty? }
	  if @products.empty?
		flash[:notice] = "Products updated"
		redirect_to products_url
	  else
		render :action => "edit_individual"
	  end
	end
	 
147) Has_many throygh association example :-

	script/generate model tag name:string
	script/generate model tagging article_id:integer tag_id:integer
	rake db:migrate

	models/tagging.rb
	class Tagging < ActiveRecord::Base
	  belongs_to :article
	  belongs_to :tag
	end

	models/tag.rb
	class Tag < ActiveRecord::Base
	  has_many :taggings, :dependent => :destroy
	  has_many :articles, :through => :taggings
	end

	models/article.rb
	class Article < ActiveRecord::Base
	  has_many :comments, :dependent => :destroy
	  has_many :taggings, :dependent => :destroy
	  has_many :tags, :through => :taggings
	  validates_presence_of :name, :content
	  attr_writer :tag_names
	  after_save :assign_tags
	  
	  def tag_names
		@tag_names || tags.map(&:name).join(' ')
	  end
	  
	  private
	  
	  def assign_tags
		if @tag_names
		  self.tags = @tag_names.split(/\s+/).map do |name|
			Tag.find_or_create_by_name(name)
		  end
		end
	  end
	end

	articles/_form.html.erb
	<p>
	  <%= f.label :tag_names %><br />
	  <%= f.text_field :tag_names %>
	</p>

148) firequark is a firefox pluggin which works with firebug to get tha CSS selector for a particular element (Railscast-173)

149) $(function(){
	   ---
	 });
	 is equal to
	 $(document).ready(function(){
	   ---
	 });
	 
150) Pagination with ajax : (Railscast-174)
		$(function() {
		  $(".pagination a").live("click", function() {    // live is used so that the links work even after new contents are fetched by ajax
			$(".pagination").html("Page is loading...");
			$.getScript(this.href);
			return false;
		  });
		});
		
	 Check Railscast-175 to get ajax pagination + restful page URL's with help of JS.
	 
151) If u want to print the log into ur rails console then set the log level as below :
	 ActiveRecord::Base.logger = Logger.new(STDOUT)
	 
152) searchlogic gem :- Searchlogic makes searching models(DB objects) easier than ever with its assortment of named scopes. 
	(Diadvantage : some security issues since it creates a url containing all the searched strings even which is not mentioned in the form. Advised only for admin pages.)
	
153) say_with_time method on the migration file displays the time taken by the set of statements written inside the block of that nethod.
	 Ex: #version_existing_pages migration
	 class VersionExistingPages < ActiveRecord::Migration
	   def self.up
		 say_with_time "Setting initial version for pages" do
		   Page.find_each(&:touch)
		 end
	   end
     end	   
	 
154) Validating attachment type using paperclip :
	 validates_attachment_content_type :photo, :content_type => ['image/jpeg', 'image/png']
	 But this can also be cracked in some ways, so we should make changes at the apache webserver level, so that any script cannot be executed. (http://www.mysql-apache-php.com/fileupload-security.htm)
	 
155) To restrict passwords to be displayed in log files use the 
     class ApplicationController < ActionController::Base
	   filter_parameter_logging :password
	 end
	 
156) Suppose there are several users and every user has certain projects and we wanr to restrict one user from accessing other users project the can do something like this :
	projects_controller.rb
	def show
	  @project = current_user.projects.find(params[:id])
	end

157) ActiveRecord joins uses INNER JOIN and
     ActiveRecord include uses LEFT OUTER JOIN
	 
158) define_method add a instance method to the class or module defining it.

159) Difference between include & extend :-
    include : mixes in specified module methods as instance methods in the target class
    extend : mixes in specified module methods as class methods in the target class
	
	module ReusableModule
	  def module_method
		puts "Module Method: Hi there!"
	  end
	end

	class ClassThatIncludes
	  include ReusableModule
	end
	class ClassThatExtends
	  extend ReusableModule
	end

	puts "Include"
	ClassThatIncludes.new.module_method       # "Module Method: Hi there!"
	puts "Extend"
	ClassThatExtends.module_method            # "Module Method: Hi there!"
	
	If you include module ReusableModule in class ClassThatIncludes, the methods, constants, classes, submodules, and other declarations gets referenced.

	If you extend class ClassThatExtends with module ReusableModule, then the methods and constants gets copied. Obviously, if you are not careful, you can waste a lot of memory by dynamically duplicating definitions.

	--> extend - adds the specified module's methods and constants to the target's metaclass (i.e. the singleton class) e.g.

    if you call Klazz.extend(Mod), now Klazz has Mod's methods (as class methods)
    if you call obj.extend(Mod), now obj has Mod's methods (as instance methods), but no other instance of of obj.class has those methods.
    extend is a public method

	--> include - By default, it mixes in the specified module's methods as instance methods in the target module/class. e.g.

    if you call class Klazz; include Mod; end;, now all instances of Klazz have access to Mod's methods (as instance methods)
    include is a private method, because it's intended to be called from within the container class/module.

	module CroppableImage
	  def self.included(base)
		base.extend(ClassMethods)
	  end

	  module ClassMethods
		def bar
		  puts 'class method'
		end
	  end

	  def foo
		puts 'instance method'
	  end
	end
	
160) To check how your application behaves in production mode set
	config/environments/development.rb
	config.consider_all_requests_local = false

161) Alternative of serialization :- bitmask index
	Consider the example of an application having users who can have many roles, then instead of serializing roles in yaml format we can also store a bitmask index for those array of roles.
	%w[admin super normal]
	for admin, super  --> 2**0 + 2**1 = 3
	for admin, normal --> 2**0 + 2**2 = 5
	for super, normal --> 2**1 + 2**2 = 6
	for admin,super,normal --> 2**0 + 2**1 + 2**2 = 7
	
	Ex: models/user.rb
	class User < ActiveRecord::Base
	  acts_as_authentic
	  has_many :articles
	  has_many :comments
	  
	  # this will allow us to fetch all the users whith the given role (User.with_role('admin'))
	  named_scope :with_role, lambda { |role| {:conditions => "roles_mask & #{2**ROLES.index(role.to_s)} > 0"} }
	  
	  ROLES = %w[admin moderator author]
	  
	  def roles=(roles)
		self.roles_mask = (roles & ROLES).map { |r| 2**ROLES.index(r) }.sum
	  end
	  
	  def roles
		ROLES.reject { |r| ((roles_mask || 0) & 2**ROLES.index(r)).zero? }
	  end
	  
	  def role_symbols
		roles.map(&:to_sym)
	  end
	end

162) Command to get all the commands u typed in 
	script/console
	puts Readline::HISTORY.entries.split("exit").last[0..-2].join("\n")

163) To override any kind of exception and display a flash error instead of the default error page, you can override that exception in the application controller

	application_controller.rb
	class ApplicationController < ActionController::Base
	  helper :all #gives access to helper module methods in the controllers
	  protect_from_forgery
	  rescue_from CanCan::AccessDenied do |exception|
	    flash[:error] = "Access denied."
	    redirect_to root_url
	  end
	end

164) rake middleware : command lists the middleware of our rails application.

165) Model without a backend database table :-

	models/recommendation.rb
	class Recommendation < ActiveRecord::Base
	  def self.columns() @columns ||= []; end
	 
	  def self.column(name, sql_type = nil, default = nil, null = true)
		columns << ActiveRecord::ConnectionAdapters::Column.new(name.to_s, default, sql_type.to_s, null)
	  end
	  
	  column :from_email, :string
	  column :to_email, :string
	  column :article_id, :integer
	  column :message, :text
	  
	  validates_format_of :from_email, :to_email, :with => /^[-a-z0-9_+\.]+\@([-a-z0-9]+\.)+[a-z0-9]{2,4}$/i
	  validates_length_of :message, :maximum => 500
	  
	  belongs_to :article
	end

	recommendations_controller.rb
	def new
	  @recommendation = Recommendation.new(:article_id => params[:article_id])
	end

	def create
	  @recommendation = Recommendation.new(params[:recommendation])
	  if @recommendation.valid?
		# send email
		flash[:notice] = "Successfully created recommendation."
		redirect_to root_url
	  else
		render :action => 'new'
	  end
	end

166) feilds_for is used for displaying associated model in the form.
     Ex:- Survey has many questions & Question has many answers
	 
	Note: If you are protecting attributes with attr_accessible be certain to add the nested attributes to that (such as questions_attributes and answers_attributes).
	
	models/survey.rb
	class Survey < ActiveRecord::Base
	  attr_accessible :name, :questions_attributes
	  has_many :questions, :dependent => :destroy
	  accepts_nested_attributes_for :questions, :reject_if => lambda { |a| a[:content].blank? }, :allow_destroy => true
	end

	# accepts_nested_attributes_for is used to manage associated records in a single form.
	
	models/question.rb
	class Question < ActiveRecord::Base
	  attr_accessible :content, :survey_id, :answers_attributes
	  belongs_to :survey
	  has_many :answers, :dependent => :destroy
	  accepts_nested_attributes_for :answers, :reject_if => lambda { |a| a[:content].blank? }, :allow_destroy => true
	end

	models/answer.rb
	class Answer < ActiveRecord::Base
	  belongs_to :question
	end

	views/surveys/_form.html.erb
	<%= form_for @survey do |f| %>
	  <%= f.error_messages %>
	  <p>
		<%= f.label :name %><br />
		<%= f.text_field :name %>
	  </p>
	  <%= f.fields_for :questions do |builder| %>
		<%= render "question_fields", :f => builder %>
	  <% end %>
	  <p><%= f.submit "Submit" %></p>
	<% end %>

	views/surveys/_question_fields.html.erb
	<fieldset>
	  <%= f.label :content, "Question" %><br />
	  <%= f.text_area :content %><br />
	  <%= f.check_box :_destroy %>
	  <%= f.label :_destroy, "Remove Question" %>
	  <%= f.fields_for :answers do |builder| %>
		<%= render 'answer_fields', f: builder %>
	  <% end %>
	  <%= link_to_add_fields "Add Answer", f, :answers %>
	</fieldset>

	views/surveys/_answer_fields.html.erb
	<fieldset>
	  <%= f.label :content, "Answer" %>
	  <%= f.text_field :content %>
	  <%= f.hidden_field :_destroy %>
	  <%= link_to "remove", '#', class: "remove_fields" %>
	</fieldset>

	surveys.js.coffee
	jQuery ->
	  $('form').on 'click', '.remove_fields', (event) ->
		$(this).prev('input[type=hidden]').val('1')
		$(this).closest('fieldset').hide()
		event.preventDefault() // since we donot want the normal link behaviour

	  $('form').on 'click', '.add_fields', (event) ->
		time = new Date().getTime()
		regexp = new RegExp($(this).data('id'), 'g')
		$(this).before($(this).data('fields').replace(regexp, time))
		event.preventDefault()

	application_helper.rb
	module ApplicationHelper
	  def link_to_add_fields(name, f, association)
		new_object = f.object.send(association).klass.new
		id = new_object.object_id
		fields = f.fields_for(association, new_object, child_index: id) do |builder|
		  render(association.to_s.singularize + "_fields", f: builder)
		end
		link_to(name, '#', class: "add_fields", data: {id: id, fields: fields.gsub("\n", "")})
	  end
	end

167) Rendering customized json response
     contoller/owners_controller.rb
	 def index
	   @owner = Owner.all
	   respond_to do |format|
	     format.html
		 fromat.json {render json: @owner}
	   end
	 end
	 
	 o/p --> @owner object in json format
	 
	 In Rails 3
	 To send a cutomized json we can use jbuilder template handler (we can use jbuilder API to build our custom json object)
	 views/owners/indev.json.builder
	 json.array!(@owners) do |owner|
	   json.extract! owner, :name
	   json.url owner_url(owner)
	 end
	 
	 Now in Rails 4 we can also write the custom json object in pure ruby
	 views/owners/indev.json.ruby
	 owner_hash = @owners.map do |owner|
	   { name: owner.name, url: owner_url(owner) }
	 end
	 owner_hash.to_json
	 
168)bundle install --without db
	This command will install all dependencies except the MySQL and PostgreSQL Ruby drivers (means database drivers).
	
169) Rails default file based cache store (ActiveSupport::Cache::FileStore) is slower.
	 That's why centralized memory based store like mem-cache is used in production servers
	 
	 config/environments/production.rb
	 config.cache_store = :mem_cache_store
	 
170) bundle check
     The above command lists any missing gems or dependencies.
	
	 bundle help
	 The above command lists the commands available for bundler.
	 
	 bundle help install
	 Gives u the help for install
	 
	 bundle install --without=production 
	 The above command  runs bundle for all gems except that are listed under production group.
	 
	 bundle outdated
	 Lists the gems whose higher versions are available than those mentioned in ur gemfile.
	 
	 Locking & Unlocking :-
	 bundle lock
	 This will lock the gemfile versions in Gemfile.lock and not allow it to be modified even on bundle install
	 
	 To update gems, modify the Gemfile, then run
	 bundle install --relock
	 
	 To bundle the gems inside your application run
	 bundle pack
	 The above command will generate .gem file inside vendor/cache
	 Next time when u run bundle install then gems will be installed from this vendor/cache directory instead of rubygems website.
	 
171) In Gemfile
     gem 'capistrano', '~> 2.11.3'
     ~> means on bundle install if higher tiny version is available then it will update it (means 2.11.4), but willnot update for higher minor version (like 2.12.0)
     ~> updates minor version if its mentioned like
     gem 'capistrano', '~> 2.11'
	 updates to 2.12
	 
172) gem 'ruby-debug19', :require => 'ruby-debug'
     It means ruby-debug.rb file has to be loaded in case the name of the gem is not matched.
	 
173) gem 'rails', github: 'rails/rails', branch: '3-2-stable', ref: 'dfdfs231abc123...'
     With option github, we can give the github_username/repo_name along with branch to be used and commit SHA as ref to be referenced.
	 
174) To reference the gems from uy system use the path option.
     gem 'rails', path: '~/code/rails'
	 
175) To avoid using bundle exec in production environment, u can use the command 
     bundle install --binstubs
     this will create a bin folder in the application which contains the executables for all the gems.
     Then rake can be used as 
     ./bin/rake db:migrate (for example)
	 instead of bundle exec rake db:migrate
	 
176) ActiveRecord query in Rails 3 (Episode - 203)
	 articles = Article.order("name") ---> Doesnot fires a  query in the DB, it just created a ActiveRecord::Relation object.
	 Query is fired when we perform other methods like all or first or each.
	 article.all.to_sql ---> Returns the SQL performed on the DB.
	 
177) Routing in Rails 3
	 match "/about.:format" => "info#about", :as => :about
	 The above line gives us the route for formatted path like
	 localhost:3000/about.pdf but not the default html.erb
	 
	 match "/about(.:format)" => "info#about", :as => :about
	 The above line enables us to use both localhost:3000/about or localhost:3000/about.pdf
	 It makes format as optional.
	 
	 # Routes with constraints
	 match "/:year(/:month(/:day))" => "info#about", :constraints => { :year => /\d{4}/, :month => /\d{2}/, :day => /\d{2}/ }
  
	 # With user_agent which is used to determine the browser
     match "/secret" => "info#about", :constraints => { :user_agent => /Firefox/ }
	
	 # For this, constraint will be applied to the routes within the block
     constraints :host => /localhost/ do
       match "/secret" => "info#about"
     end
  
	 # Rack app route
     match "/hello" => proc { |env| [200, {}, "Hello Rack!"] }
	 
178) XSS Protection in Rails 3 :- (Railscast - 204)
     By default  <p><%= comment.content %></p> is already escaped , there is no need to place h method. But can also place it.
	 
	 # rails c
	 "foo".html_safe?  --> false
	 safe = "safe".html_safe
	 safe.html_safe?   --> true
	 
	 Example to use both h and html_safe method in helper method to create a link :
	 
	views/comments/_comment.html.erb
	<div class="comment">
	  <%= strong link_to(comment.name, comment.url) %>
	  <p><%= comment.content %></p>
	</div>

	application_helper.rb
	def strong(content)
	  "<strong>#{h(content)}</strong>".html_safe
	end

	The h method in the helper method escaped any script or tag if present and the html_safe method to mark it as html safe.

        #html_safe marks a string HTML-safe. It’s a common misconception that this method makes the string safe, it doesn’t. If you know that the string is safe, you can call this method, but it will only set the HTML-safe flag. So you should never do <%= params[:user_input].html_safe %>. Use the h() method to make it real HTML-safe.

        The raw() method is similar to the html_safe method. So you should never do: <%= raw params[:user_input] %>
        raw = to_string + html_safe

        This is how the string concatenation methods (+, concat(), <<) work:
        If the left side is HTML-unsafe or the right side is HTML-safe, then it works like normal string concatenation and keeps the HTML-safe flag of the left side
        Otherwise it will HTML-escape the right side and add it to the string

179) Unobtrusive Javascript is a way to seperate out javascript from html document, so that we may not place javascript code directly inline.

180) Purpose of javascript include tag and CSRF meta tag :-
	 <%= javascript_include_tag :defaults %>
	 <%= csrf_meta_tag %>

	 To include default js like jquery.js in rails 3 app, we write <%= javascript_include_tag :defaults %> so that jquery gets loaded in all the pages.
	 
	 <%= csrf_meta_tag %> helper method outputs the meta tag for the authenticity token which is necessary to submit requests like delete request or other requests so that authenticity is guaranteed. This is necessary to prevent cross-site request forgery (means any delete or post request is coming from an authenticated user but not from another site or hacker).
	 
181) A way to put * on mandatory feilds using a helper method and method provided by ActiveModel::Validations module :
	 >> User.validators  --> lists validations applied for user model
	 
	 <div class="field">
		<%= f.label :email %><%= mark_required(@user, :email) %><br />
		<%= f.text_field :email %>
	 </div>
	 
	application_helper.rb
	def mark_required(object, attribute)
	  "*" if object.class.validators_on(attribute).map(&:class).include? ActiveModel::Validations::PresenceValidator
	end
	
182) @products = Product.scoped
	 The above line is similar to Product.all but in .all a query is triggered to the DB where as .scoped method doesnot fires a query, it just tells that additional conditions can be added before executing a query.
	 Ex:
      def index
		@products = Product.scoped
		@products = @products.where("name like ?", "%" + params[:name] + "%") if params[:name]
		@products = @products.where("price >= ?", params[:price_gt]) if params[:price_gt]
		@products = @products.where("price <= ?", params[:price_lt]) if params[:price_lt]
	  end
	
	  http://localhost:3000/products?name=video&price_gt=50   -->  Returns Products name containing video having price >= 50.
	  
	  To chain multiple conditions, you should create a delegator class --> (Refer Railscasts - 212)
	  
183) Creating class using Struct.new and use of delegate method :-
	 
	helpers/calendar_helper.rb
	module CalendarHelper
	  def calendar(date = Date.today, &block)
		Calendar.new(self, date, block).table
	  end

	  class Calendar < Struct.new(:view, :date, :callback)
		HEADER = %w[Sunday Monday Tuesday Wednesday Thursday Friday Saturday]
		START_DAY = :sunday

		delegate :content_tag, to: :view

		def table
		  content_tag :table, class: "calendar" do
			header + week_rows
		  end
		end

		def header
		  content_tag :tr do
			HEADER.map { |day| content_tag :th, day }.join.html_safe
		  end
		end
	end
	
	In the above example,
	Calendar class inherits from a new Struct which is a convenient way do define accessors for the various attributes. The first attribute here is the view and it’s important to pass this in as we don’t have access to the helper methods in our class. We can easily delegate to the view for any helper methods we want to access in the calendar or maybe override method_missing in here.

184) To check whether a robot is hitting your server :-
     request.user_agent =~ /\b(Baidu|Gigabot|Googlebot|libwww-perl|lwp-trivial|msnbot|SiteUptime|Slurp|WordPress|ZIBB|ZyBorg)\b/i
	 
185) Whenever we are writing the condition in a query in the form of string then we should always add the table name in column name to avoid ambiguity.
     If we are using hash to write the condition then rails will add the table name, we need not worry about it.
	 
	Ex :-
	scope :discontinued, where(:discontinued => true)

	def self.cheaper_than(price)
	  where("products.price < ?", price)
	end
	
186) If we want to join a join query and a scope then there are 2 ways to do it :-

	Ex:-
	ruby-1.8.7-p249 > Product.cheap.to_sql
	=> "SELECT    \"products\".* FROM      \"products\" WHERE    (price < 5)"
	
	ruby-1.8.7-p249 > Category.joins(:products).to_sql
	=> "SELECT     \"categories\".* FROM       \"categories\" INNER JOIN \"products\" ON \"products\".\"category_id\" = \"categories\".\"id\""
	
	If we want to join the above queries then either we can use merge method :-
	Category.joins(:products).merge(Product.cheap)
	
	OR (use & which is an alias for merge method)
	
	Category.joins(:products) & Product.cheap
	
	(Category.joins(:products) & Product.cheap).to_sql
	=> "SELECT     \"categories\".* FROM       \"categories\" INNER JOIN \"products\" ON \"products\".\"category_id\" = \"categories\".\"id\" WHERE     (price < 5)"
	
187) Product.discontinued  --> Gives products list which are discontinued
	 => [#<Product id: 3, name: "Some DVD", price: 13.49, discontinued: true, category_id: 1, created_at: "2010-05-25 19:45:05", updated_at: "2010-05-25 19:45:05">]
	 
	 As the named scope uses a hash we can call the build method on it to build a new product with its discontinued attribute already set to true.
	 p = Product.discontinued.build
	 => #<Product id: nil, name: nil, price: nil, discontinued: true, category_id: nil, created_at: nil, updated_at: nil>

188) Arel :-
	 Arel drives ActiveRecord queries under the bonnet.
	 To access Arel directly in Rails 3 we can access an arel_table so we’ll get the arel_table for the Product model in the console and assign it to a variable.
	 > t = Product.arel_table
	 t[:price]
	 => <Attribute price>
	 t[:price].eq(2.99)
	 => #<Arel::Predicates::Equality:0x1040dd9f0 @operand1=<Attribute price>, @operand2=2.99>
	 > t[:name].matches('%lore').to_sql
	 => "\"products\".\"name\" LIKE '%lore'"
	 t[:price].eq(2.99).or(t[:name].matches('%lore'))
	 > t[:price].eq(2.99).or(t[:name].matches('%lore')).to_sql
	 => "(\"products\".\"price\" = 2.99 OR \"products\".\"name\" LIKE '%lore')"
	 
	 We can pass predicates as arguments to an ActiveRecord where call. This means that we can pass the predicate we’ve created to Product.where to return all of the products whose price is £2.99 or whose name ends in ‘lore’.
	 Product.where(t[:price].eq(2.99).or(t[:name].matches('%lore')))
	 
	 There are a number of plugins now available that take the power of Arel and put it into a more convenient interface such as MetaWhere. This allows you to access Arel methods such as matches and eq inside the conditions hash like this:
	 Ex:- Product.where(:price.eq => 2.99, :name.matches => '%lore')

189) XSS :-
	 ------
	As of Rails 3, values interpolated into a template are automatically escaped. Escaping refers to turning something like "<script>" into "&lt;script&gt;". This renders the tag harmless, since the browser now sees it as simple text to display and will not execute it.
 
	Rails' automatic escaping is accomplished by giving all strings an `html_safe` boolean which defaults to false. When Rails renders a string, it performs escaping on any whose boolean is not true. Developers who are certain that a certain string will not contain user input can call `#html_safe` on it, which sets the boolean to true.
 
	That last sentence is important: only call `#html_safe` on strings which you're certain will not contain unescaped user input. 
 
	Where you can still be vulnerable
 
	Since Rails does a great job at protecting you from XSS, the biggest danger lies in inadvertently disabling this protection.
 
	Imagine you've written a helper to display a bolded version of a user's name:
 
    def strong_user_name(user)
      "<strong>#{user.name}</strong>"
    end
 
	Reloading the page, you see that Rails has escaped your strong tags. Unthinking, you quickly append ".html_safe" to the end of your returned string and verify the user's name now displays correctly.
 
	Welcome to Ownedville, population you. If users can specify their own names, it's only a matter of time before one of your users changes his legal name to "<script>copyOutSomeCookies</script>".
 
	Here's what you should have done:
 
    def strong_user_name(user)
      "<strong>#{h user.name}</strong>".html_safe
    end
 
	The call to `#h` forces escaping on the user's name.
 
	Or, you could have used Rails' built-in `#content_tag`:
 
    def strong_user_name(user)
      content_tag(:strong, user.name)
    end
 
	Either would have prevented your eventual tears.
	
190) Ruby Dev-Ops cheat sheat :- 
	http://rubytune.com/cheat
	
191) MySQL user creation & grant privileges :-
     A good view of all users and their approximate privileges is shown by the below query. If there is a password, it will by an encrytped string; if not, this field is blank. Select is a very general privilege; insert allows table manipulation within a database; shutdown allows major system changes, and should only be usable by root; the ability to grant permissions is separate from the others.

	SELECT user, host, password, select_priv, insert_priv, shutdown_priv, grant_priv FROM mysql.user;

	View permissions for individual databases.

	SELECT user, host, db, select_priv, insert_priv, grant_priv FROM mysql.db;

	User creation & granting privileges :-
	--------------------------------------
	CREATE USER 'carlos'@'localhost' IDENTIFIED BY 'p@$$w3rd';

	But now if you drop this user & try to recreate it then u will get an error like 
	ERROR 1396 (HY000): Operation CREATE USER failed for 'user_name'@'localhost'

	So, its a bug in MySQL, to rectify it first, drop user then flush privilges the recreate that user.

	drop user 'carlos'@'localhost';
	flush privileges;
	create user 'carlos'@'localhost' identified by 'p@$$w3rd'

	GRANT SELECT ON user_name.* TO 'carlos'@'localhost' IDENTIFIED BY 'p@$$w3rd' WITH GRANT OPTION;

	SELECT user, host, password, select_priv, insert_priv, shutdown_priv, grant_priv  FROM mysql.user;
	--> this will show N ,N, N, N  (since its showing global privileges for *.*)

	Instead we have to check at mysql.db table using the below query.

	select * from mysql.db where user='user_name' and host='localhost' and db='db_name'\G
	--> *************************** 1. row ***************************
                 Host: localhost
                   Db: db_name
                 User: user_name
          Select_priv: Y
          Insert_priv: Y
          Update_priv: Y
          Delete_priv: Y
          Create_priv: Y
            Drop_priv: Y
           Grant_priv: Y
      References_priv: Y
           Index_priv: Y
           Alter_priv: Y
Create_tmp_table_priv: Y
     Lock_tables_priv: Y
     Create_view_priv: Y
       Show_view_priv: Y
  Create_routine_priv: Y
   Alter_routine_priv: Y
         Execute_priv: Y
           Event_priv: Y
         Trigger_priv: Y

192) To make json api, we should onlu use respond_to :json at the top in the class.
     Ex :
	 # app/controllers/api/feeds_controller.rb
	class Api::FeedsController < ApplicationController
	  respond_to :json

	  def index
        feeds = Feed.rss
		respond_with feeds, each_serializer: FeedSerializer
	  end

      def show
        feeds = Feed.where(id: params[:id]).rss
		respond_with feeds, each_serializer: FeedSerializer
      end
	end
	
193) We can manipulate multiple elements using gsub :
	def geekify(string)
      string.gsub(/[leto]/, 'l' => '1', 'e' => '3', 't' => '7', 'o' => '0')
	end

	geekify('leet') # => '1337'
	geekify('noob') # => 'n00b'

	def doctorize(string)
	  string.gsub(/M(iste)?r/, 'Mister' => 'Doctor', 'Mr' => 'Dr')
	end

	doctorize('Mister Freeze') # => 'Doctor Freeze'
	doctorize('Mr Smith')   # => 'Dr Smith'

194) :dependent => :destroy or :dependent => :delete_all in the association declaration. The former will run callbacks in the association and the later one does not.

195) Please do not close and reopen pull-requests for the same topic. Simply modify the commits using git commit --amend or git rebase -i and then force push to github (git push -f). This will update the Pull Requests with your modifications. If you close and reopen the discussion is spread across and it's hard to follow. It generates more noise than necessary.

196) Browser Console Tricks :-
    i) console.table() can be used to output data from an array of arrays or a list of objects in a sortable, tabular format.
   ii) A timer can be started in the console by using console.time(label). The string label is needed so we have a reference to the timer when we want to stop it. The timer is stopped by calling console.timeEnd(label), which will output to the console the time in milliseconds since the timer (identified by label) was started.
  iii) If you need the result of the previous expression for your next console evaluation, you can use the variable $_, which is automatically set to the last expression result for you.
   iv) You can automatically create a breakpoint in your code by adding the following line to your JavaScript: debugger; . This will automatically create a breakpoint in the code when it is run with Developer Tools open.
	   Although useful for quickly adding breakpoints without having to find the line in the Developer Tools, be careful not to send code with debugger; live.
	   
197) ActiveModel contains all the code related to table-less model (Ex: Validations..etc). ActiveRecord heavily depends upon ActiveModel.
The non-database functionality of Active Record is extracted out into Active Model

198) Redirecting route to a new path whose name is same as that of existing route :- Redirecting about to aboutus(new path)
     match "/about" => redirect("/aboutus")
	 match "/aboutus" => "info#about"
	 
199) Creating a smaller Rack Application for faster performance :- (Railscasts - 222)
     routes.rb:-
	 -----------
	 match "/processes" => ProcessesApp.action(:index)  #--> ProcessApp (Rack App)
	 
	 
	lib/processes_app.rb:-
	----------------------
	class ProcessesApp < ActionController::Metal
		include ActionController::Rendering   #--> WIth this we can use erb template rendering in this lib dir
  
		append_view_path "#{Rails.root}/app/views"  #--> With this line we r telling from where to pick the view files
  
		def index
			@processes = `ps -axcr -o "pid,pcpu,pmem,time,comm"`
			render
		end
	end

	app/views/processes_app/index.html.erb:-
	----------------------------------------
	<h1>Processes</h1>
	<pre><%= @processes %></pre>

200) date function of sql is used to convert the created_at stored in our database to date.
	  def self.total_on(date)
		where("date(purchased_at) = ?",date).sum(:total_price)
	  end
	  
201) Inline flash notice with redirect_to
	 redirect_to @product, :notice => "Successfully created product."
	 
202) Shortcut for edit_product_path(@product)  -->  [:edit, @product]
	 This is similar to the path written for nested resource [@category, @product] --> for show page

203) cookies[:last_product_id] = @product.id  --> Expires when the user closes the browser window.
	 cookies.permanent[:last_product_id] = @product.id  --> Has expiry of 20 Yrs.
	 
204) "Remember me" functionality :- (http://m.onkey.org/signed-and-permanent-cookies-in-rails-3)

	# User.rb
	def self.authenticated_with_token(id, stored_salt)
	  u = find_by_id(user_id)
	  u && u.salt == stored_salt ? u : nil
	end

	And when the user checks “Remember me” box, make sure the following gets run :

	cookies.permanent.signed[:remember_me] = [current_user.id, current_user.salt]

	This will set a permanent and signed cookie using the secret specified in ActionController::Base.cookie_verifier_secret. If you don’t have the cookie_verifier_secret defined, you might want to do that in one of the initializers.

	Now when you want to login using the cookie :

	user = User.authenticated_with_token(*cookies.signed[:remember_me])

	In this specific case, it’s very important to use the salt in the cookie value. That makes sure the cookie gets invalidated if the user changes his password.
	
205) Shortcut for respond_to   ---> (Railscast - 224) -- See for detailed usage
    class Product
	  def index
	    @products = Product.all
		respond_to do |format|
		  format.html
		  format.xml { render :xml => @products }
		end
	  end
	end
	
	Can be written as 
	
	class Product
	  respond_to :html, :xml
	  
	  def index
	    @products = Product.all
		respond_with(@products)
	  end
	end
	
	URL should end with correct format for the type of response required.
	For XML :- http://localhost:3000/products.xml

206) Dynamic content in config yml file

	config/locales/en.yml
	---------------------
	en:
	  flash:
		actions:
		  create:
			notice: "Your %{resource_name} has been created!"

207) rake stats ---> Gives you the statistics related to your project.

208) match 'products/recent'   (This is short-hand option)
	 # same as
	 match 'products/recent', :to =>'products#recent', :as => 'products_recent'

209) For inspecting a large content in the browser itself :
	 render :text => params.inspect
	 OR
	 raise params.inspect

210) To disable mass assignment in rails 3 for only some cases : use without_protection: true  
	 Post.new(params[:post], without_protection: true)  -- Try it out
	 OR
	 def self.new_with_session(params, session)
	  if session["devise.user_attributes"]
		new(session["devise.user_attributes"], without_protection: true) do |user|
		  user.attributes = params
		  user.valid?
		end
	  else
		super
	  end
	end

211) In a user form, to access say user object's method(password_required?) use f.object
	<% if f.object.password_required? %>
	  ...
	<% end %>

212) If you want to create a mthod with chainable scope with if else condition then use scoped method for non-matching condition, otherwise it will return nil :

	def self.search(search)
	  if search
		where('name LIKE ?', "%#{search}%")
	  else
		scoped
	  end
	end

213) To submit form input fields on ajax form submit, use serialize method in jQuery : (Railscasts - 240)

	<%= form_tag products_path, :method => 'get', :id => "products_search" do %>
	  <p>
		<%= text_field_tag :search, params[:search] %>
		<%= submit_tag "Search", :name => nil %>
	  </p>
	  <div id="products"><%= render 'products' %></div>
	<% end %>

	$("#products_search").submit(function() {
		$.get($("#products_search").attr("action"), $("#products_search").serialize(), null, "script");
		return false; # To prevent form submission (Page refresh)
	});

214) To load the rails environment at a place where its not loaded : say inside a custom config file
	require File.expand_path("../environment", __FILE__)

215) Tales OS should be used by journalists (For security purpose)

216) Always use : flash.now with render & flash[:notice]/flash[:error] with redirects.
	def create
	  user = User.authenticate(params[:email], params[:password])
	  if user
		session[:user_id] = user.id
		redirect_to root_url, :notice => "Logged in!"
	  else
		flash.now.alert = "Invalid email or password"
		render "new"
	  end
	end

217) number.replace(/[ -]/g, '')
	 /g is used in regex to replace multiple occurences of say here in this example space & '-'.

218) view_context :- An instance of a view class. The default view class is ActionView::Base.
     view_context is used in controller to access ActionView::Base methods.

219) Converting Hash to json in js.erb template :
     <%
	response = {
		:success => @success,
		:data    => @feed_comment,
		:unread_count => current_user.whats_new_count,
	        :feed_id => @feed.id,
	        :feed_updates => @feed_updates,
	        :html    => render( :partial => '/ce/pulse/feed/comment', :locals => {:feed => @feed, :comment => @feed_comment, :new_record => true})
	    }
     %>

     var resp<%= "= #{response.to_json}".html_safe %>

220) gem 'uglifier' --> is used to compress the assets in production

221) :multipart => true options is no longer required after 3.1+ if you are using file_field in your form.

222) If we are not streaming a rails application then : first the view file is rendered and then the layout.
     For ex:-
	 view file --> <% @title = 'Page Title' %>
	 layout -----> <title><%= @title%></title>   will work

	 But in streaming, first the layout is rendered and then the view file.

223) To access a partial from any of the views folder like say products, stores, items etc :- (Railscasts :- 269)
     create a folder named application (behaves just like application controller) in views folder and then any file placed inside application will be accessible from any views folder.

224) Template Inheritance works just like inheritance in controllers.
     If a file is placed in a folder named say employees and mangers & staffs controllers inherit form employees_controller then any file placed inside employees views folder will be accessible to mangers & staffs views folder.

225) Basic user authentication without any gem can easily achived in Rails 3.1+ using has_secure_password method which gives a nice way to handle authentication. (Railscasts :- 270)
      Also in Rails 3.1+ if we want to force ssl on any page then we can use force_ssl method in the controllers to redirect the user forcefully to https url.

226) An example of after validation :
	Geocoder Example :-
	geocoded_by :address
	after_validation :geocode, :if => :address_changed? # means geocode the address if address is changed

227) Splat Operator in Ruby :-
	The splat operator can be used in a case statement :

	WILD = ['lion','gnu']
	TAME = ['cat','cow']

	case animal
    when *WILD
	  "Run"
	when *TAME
	  "Catch"
	end

	And it can be used to convert a hash into an array:
	>> a = *{:a=>1,:b=>2}
	=> [[:a,1],[:b,2]]
	>> Hash[*a.flatten]
	=> {:a=>1,:b=>2}

228) scores = {
	  'The Lady' => 3,
	  'Fate' => 2,
	  'Death' => 10
	}
	You want to to sort them by scores. You can do it with:

	leaderboard = scores.sort_by { |_, score| -score }
	IRB Output:

	=> [["Death", 10], ["The Lady", 3], ["Fate", 2]]

229) We can run our rake tasks parallely by running it with -m option. m stands for multitasking.
	 rake -m
	 To see how much time the rake task has taken run
	 time rake -m

230) Array([1,2,3])
	 # => [1,2,3]

	 Array(nil)
	 # => []
	 Notice in the second example that when we pass nil it creates an empty array. (This avoids issues like undefined method each for nil class)
	 Array(params[:ids]).each do |id|
	   # ...
	 end
	 
231) Offline Browsing inside Google Chrome

	While inside Chrome, type chrome://flags/#enable-offline-mode in the address bar, click “Enable” and restart your browser. Your Chrome will no longer serve the “not connected to the Internet” error if the page you are trying to access is available in the local cache.

	Google Chrome caches the HTML content, images, JavaScript and the CSS stylesheets associated with a page so your offline copy should not look very different from the original. However, if there are resources that require an active Internet connection, like JavaScript widgets or videos, they’ll be replaced with placeholder images.

232) Converting numbers in string to actual numeric object
    Ex : "12" to 12
         "17.11" to 17.11

    Integer(str) rescue return false  ==> Converts both positives & negatives integers
    Float(str) rescue return false  ==> Converts both positives & negatives floats
    Ex: Integer("12") => 12
		Interger("-10") => -10
        Float("17.11") => 17.11

    str =~ /\D/ ? nil : str.to_i   => To convert only postive integers, others nil.

233) When eager loading fires IN query & when it JOINS :
     When you load an author with all associated books Active Record will make multiple queries like this:

    Author.includes(:books).where(:name => ['bell hooks', 'Homer').to_a

    => SELECT `authors`.* FROM `authors` WHERE `name` IN ('bell hooks', 'Homer')
    => SELECT `books`.* FROM `books` WHERE `author_id` IN (2, 5)

    Active Record saves the ids of the records from the first query to use in the second. Depending on the number of associations involved there can be arbitrarily many SQL queries made.

    However, if there is a WHERE clause that spans across tables Active Record will fall back to a slightly more resource-intensive single query:

      SELECT * FROM `authors`
      LEFT OUTER JOIN `books` ON `authors`.`id` =  `books`.`author_id`
      WHERE `authors`.`name` IN ('bell hooks', 'Homer')

    This could result in many rows that contain redundant data and it performs poorly at scale and is therefore only used when necessary.

234) Ruby calls the methods that are unique to an object singleton methods.
	 Immutable objects:- instances of Fixnum, for example will not cooperate with attempts to add singleton methods to them.

	 Singleton class is actually the first place where Ruby looks when you call a method, so any method defined in the singleton class will override the methods in the regular class.

235) Variables related to regular expressions matching, example:

    $& - text matched by regex
    $` - text preceding the match
    $' - text following the match
    $1, $2, $3 ... $n - text matched by nth group

	Some other useful variables :
    $* - alias of ARGV, read-only
    $$ - PID of current process
    $? - exit status of the last terminated process

	http://www.tutorialspoint.com/ruby/ruby_predefined_variables.htm

236) How to create a password prompt:
	 require 'io/console'
	 print 'Password: '
	 password = ((STDIN.tty? ? STDIN.noecho(&:gets) : gets) || '').chop

237) To concat a common strinh to a attribute
     select concat_ws('', '@', mention) from users;

238) $rails_rake_task can be used to determine if the action is invoked from a rake task.

239) MySQL conditional update query : (Single update for different rows)
     http://www.karlrixon.co.uk/writing/update-multiple-rows-with-different-values-and-a-single-sql-query/

240) Serving a file from the public directory means that it will always take precedence over any dynamic route in your application.

241) render :text misdirect people to think that it would render content with text/plain MIME type.
     However, render :text actually sets the response body directly, and inherits the default response MIME type, which is text/html.

     In order to reduce confusion, 3 more render format to render are introduced:

     render html: '<strong>HTML String</strong>' # render with `text/html` MIME type

     render plain: 'plain text' # render with `text/plain` MIME type

     render body: 'raw body' # render raw content, does not set content type, inherits
                             # default content type, which currently is `text/html`

     We want to phrase out the usage of render :text, to reduce the confusion in the future. There's currently no plan for deprecating render :text.

242) For per-request (threadsafe) Time zone setter : use
     time.in_time_zone(user.time_zone) in the view

243) Log file rotation in Ruby :
     In config/application.rb or one of env file
     config.logger = Logger.new(config.paths['log'].first, 5, 20*1024)
     # 5 files each of 20 MB

244) Instead of to_sql use capture_sql to get the actual SQL query :
     capture_sql command is used to make assertions against the sql run against the database.

245) Stubbing time for RSpec
     Time.stub(:now).and_return(@time)
     @time.stub(:utc).and_return(Time.utc(2016, 3, 5))
     DateTime.stub(:now).and_return(@date_time)
     @date_time.stub(:utc).and_return(DateTime.parse(Time.utc(2016, 3, 5).to_s))