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<a class="post-title-link" href="/2019/03/25/const-static-extern简介/" itemprop="url">const,static,extern简介</a></h1>
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<p>#const与宏的区别（面试题）:</p>
<ul>
<li>const简介:之前常用的字符串常量，一般是抽成宏，但是苹果不推荐我们抽成宏，推荐我们使用const常量。<ul>
<li>编译时刻:宏是预编译（编译之前处理），const是编译阶段。</li>
<li>编译检查:宏不做检查，不会报编译错误，只是替换，const会编译检查，会报编译错误。</li>
<li>宏的好处:宏能定义一些函数，方法。 const不能。</li>
<li>宏的坏处:使用大量宏，容易造成编译时间久，每次都需要重新替换。<br>注意:很多Blog都说使用宏，会消耗很多内存，我这验证并不会生成很多内存，宏定义的是常量，常量都放在常量区，只会生成一份内存。 </li>
</ul>
</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">// 常见的常量：抽成宏</span><br><span class="line">#define XMGAccount @"account"</span><br><span class="line"></span><br><span class="line">#define XMGUserDefault [NSUserDefaults standardUserDefaults]</span><br><span class="line"></span><br><span class="line">// 字符串常量</span><br><span class="line">static NSString * const account = @"account";</span><br><span class="line"></span><br><span class="line">- (void)viewDidLoad {</span><br><span class="line"> [super viewDidLoad];</span><br><span class="line"></span><br><span class="line"> // 偏好设置存储</span><br><span class="line"> // 使用宏</span><br><span class="line"> [XMGUserDefault setValue:@"123" forKey:XMGAccount];</span><br><span class="line"></span><br><span class="line"> // 使用const常量</span><br><span class="line"> [[NSUserDefaults standardUserDefaults] setValue:@"123" forKey:account];</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>#const作用：限制类型</p>
<ul>
<li>1.const仅仅用来修饰右边的变量（基本数据变量p，指针变量*p）</li>
<li><p>2.被const修饰的变量是只读的。</p>
</li>
<li><p>const基本使用</p>
</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br></pre></td><td class="code"><pre><span class="line">- (void)viewDidLoad {</span><br><span class="line"> [super viewDidLoad];</span><br><span class="line"></span><br><span class="line"> // 定义变量</span><br><span class="line"> int a = 1;</span><br><span class="line"></span><br><span class="line"> // 允许修改值</span><br><span class="line"> a = 20;</span><br><span class="line"></span><br><span class="line"> // const两种用法</span><br><span class="line"> // const:修饰基本变量p</span><br><span class="line"> // 这两种写法是一样的，const只修饰右边的基本变量b</span><br><span class="line"> const int b = 20; // b:只读变量</span><br><span class="line"> int const b = 20; // b:只读变量</span><br><span class="line"></span><br><span class="line"> // 不允许修改值</span><br><span class="line"> b = 1;</span><br><span class="line"></span><br><span class="line"> // const:修饰指针变量*p，带*的变量，就是指针变量.</span><br><span class="line"> // 定义一个指向int类型的指针变量，指向a的地址</span><br><span class="line"> int *p = &a;</span><br><span class="line"></span><br><span class="line"> int c = 10;</span><br><span class="line"></span><br><span class="line"> p = &c;</span><br><span class="line"></span><br><span class="line"> // 允许修改p指向的地址，</span><br><span class="line"> // 允许修改p访问内存空间的值</span><br><span class="line"> *p = 20;</span><br><span class="line"></span><br><span class="line"> // const修饰指针变量访问的内存空间，修饰的是右边*p1，</span><br><span class="line"> // 两种方式一样</span><br><span class="line"> const int *p1; // *p1：常量 p1:变量</span><br><span class="line"> int const *p1; // *p1：常量 p1:变量</span><br><span class="line"></span><br><span class="line"> // const修饰指针变量p1</span><br><span class="line"> int * const p1; // *p1:变量 p1:常量</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> // 第一个const修饰*p1 第二个const修饰 p1</span><br><span class="line"> // 两种方式一样</span><br><span class="line"> const int * const p1; // *p1：常量 p1：常量</span><br><span class="line"></span><br><span class="line"> int const * const p1; // *p1：常量 p1：常量</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h1 id="const开发中使用场景"><a href="#const开发中使用场景" class="headerlink" title="const开发中使用场景:"></a>const开发中使用场景:</h1><ul>
<li>1.当一个方法参数只读</li>
<li>2.定义只读全局变量</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line">@implementation ViewController</span><br><span class="line"></span><br><span class="line">// 定义只读全局常量</span><br><span class="line">NSString * const str = @"123";</span><br><span class="line"></span><br><span class="line">// 当一个方法的参数，只读.</span><br><span class="line">- (void)test:(NSString * const)name</span><br><span class="line">{</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">// 指针只读,不能通过指针修改值</span><br><span class="line">- (void)test1:(int const *)a{</span><br><span class="line"></span><br><span class="line">// *a = 10;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">// 基本数据类型只读</span><br><span class="line">- (void)test2:(int const)a{</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">@end</span><br></pre></td></tr></table></figure>
<h1 id="static和extern简单使用-要使用一个东西，先了解其作用"><a href="#static和extern简单使用-要使用一个东西，先了解其作用" class="headerlink" title="static和extern简单使用(要使用一个东西，先了解其作用)"></a>static和extern简单使用(要使用一个东西，先了解其作用)</h1><ul>
<li><p>static作用:</p>
<ul>
<li>修饰局部变量：</li>
</ul>
<ol>
<li><p>延长局部变量的生命周期,程序结束才会销毁。</p>
</li>
<li><p>局部变量只会生成一份内存,只会初始化一次。</p>
</li>
</ol>
<ul>
<li>修饰全局变量</li>
</ul>
<ol>
<li>只能在本文件中访问,修改全局变量的作用域,生命周期不会改</li>
</ol>
</li>
<li><p>extern作用:</p>
<ul>
<li>只是用来获取全局变量(包括全局静态变量)的值，不能用于定义变量</li>
</ul>
</li>
<li>extern工作原理:<ul>
<li>先在当前文件查找有没有全局变量，没有找到，才会去其他文件查找。</li>
</ul>
</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line">// 全局变量：只有一份内存，所有文件共享，与extern联合使用。</span><br><span class="line">int a = 20;</span><br><span class="line"></span><br><span class="line">// static修饰全局变量</span><br><span class="line">static int age = 20;</span><br><span class="line"></span><br><span class="line">- (void)test</span><br><span class="line">{</span><br><span class="line"> // static修饰局部变量</span><br><span class="line"> static int age = 0;</span><br><span class="line"> age++;</span><br><span class="line"> NSLog(@"%d",age);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">- (void)viewDidLoad {</span><br><span class="line"> [super viewDidLoad];</span><br><span class="line"> // Do any additional setup after loading the view, typically from a nib.</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> [self test];</span><br><span class="line"> [self test];</span><br><span class="line"></span><br><span class="line"> extern int age;</span><br><span class="line"> NSLog(@"%d",age);</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<h1 id="static与const联合使用"><a href="#static与const联合使用" class="headerlink" title="static与const联合使用"></a>static与const联合使用</h1><ul>
<li>static与const作用:声明一个只读的静态变量</li>
<li>开发使用场景:在一个文件中经常使用的字符串常量，可以使用static与const组合</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line">// 开发中常用static修饰全局变量,只改变作用域</span><br><span class="line"></span><br><span class="line">// 为什么要改变全局变量作用域，防止重复声明全局变量。</span><br><span class="line"></span><br><span class="line">// 开发中声明的全局变量，有些不希望外界改动，只允许读取。</span><br><span class="line"></span><br><span class="line">// 比如一个基本数据类型不希望别人改动</span><br><span class="line"></span><br><span class="line">// 声明一个静态的全局只读常量</span><br><span class="line">static const int a = 20;</span><br><span class="line"></span><br><span class="line">// staic和const联合的作用:声明一个静态的全局只读常量</span><br><span class="line"></span><br><span class="line">// iOS中staic和const常用使用场景，是用来代替宏，把一个经常使用的字符串常量，定义成静态全局只读变量.</span><br><span class="line"></span><br><span class="line">// 开发中经常拿到key修改值，因此用const修饰key,表示key只读，不允许修改。</span><br><span class="line">static NSString * const key = @"name";</span><br><span class="line"></span><br><span class="line">// 如果 const修饰 *key1,表示*key1只读，key1还是能改变。</span><br><span class="line"></span><br><span class="line">static NSString const *key1 = @"name";</span><br></pre></td></tr></table></figure>
<h1 id="extern与const联合使用"><a href="#extern与const联合使用" class="headerlink" title="extern与const联合使用"></a>extern与const联合使用</h1><ul>
<li>开发中使用场景:在多个文件中经常使用的同一个字符串常量，可以使用extern与const组合。</li>
<li>原因:<ul>
<li>static与const组合：在每个文件都需要定义一份静态全局变量。</li>
<li>extern与const组合:只需要定义一份全局变量，多个文件共享。</li>
</ul>
</li>
<li>全局常量正规写法:开发中便于管理所有的全局变量，通常搞一个GlobeConst文件，里面专门定义全局变量，统一管理，要不然项目文件多不好找。</li>
</ul>
<ul>
<li>GlobeConst.h</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">/*******************************首页****************************/</span><br><span class="line"></span><br><span class="line">extern NSString * const nameKey = @"name";</span><br><span class="line"></span><br><span class="line">/*******************************首页****************************/</span><br><span class="line">GlobeConst.m</span><br><span class="line">#import <Foundation/Foundation.h></span><br><span class="line"></span><br><span class="line">/*******************************首页****************************/</span><br><span class="line"></span><br><span class="line">NSString * const nameKey = @"name";</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">/*******************************首页****************************/</span><br></pre></td></tr></table></figure>
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<a class="post-title-link" href="/2019/03/25/iOS9新特性之关键字/" itemprop="url">iOS9新特性之关键字</a></h1>
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<h2 id="iOS9新出的关键字-用来修饰属性-或者方法的参数-方法的返回值"><a href="#iOS9新出的关键字-用来修饰属性-或者方法的参数-方法的返回值" class="headerlink" title="iOS9新出的关键字:用来修饰属性,或者方法的参数,方法的返回值"></a>iOS9新出的关键字:用来修饰属性,或者方法的参数,方法的返回值</h2><ul>
<li><p>好处:</p>
<ul>
<li><p>迎合swift</p>
</li>
<li><p>提高我们开发人员开发规范,减少程序员之间交流</p>
</li>
</ul>
</li>
<li><p>注意:</p>
<ul>
<li>iOS9新出关键字<code>nonnull,nullable,null_resettable,_Null_unspecified</code>只能修饰对象,不能修饰基本数据类型. </li>
<li>nullable`作用:表示可以为空</li>
</ul>
</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">nullable书写规范:</span><br><span class="line">// 方式一:</span><br><span class="line">@property (nonatomic, strong, nullable) NSString *name;</span><br><span class="line">// 方式二:</span><br><span class="line">@property (nonatomic, strong) NSString *_Nullable name;</span><br><span class="line">// 方式三:</span><br><span class="line">@property (nonatomic, strong) NSString *__nullable name;</span><br></pre></td></tr></table></figure>
<ul>
<li><code>nonnull</code>作用:不能为空</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">nonnull: non:非 null:空</span><br><span class="line"></span><br><span class="line">书写格式:</span><br><span class="line"> @property (nonatomic, strong, nonnull) NSString *icon;</span><br><span class="line"></span><br><span class="line"> @property (nonatomic, strong) NSString * _Nonnull icon;</span><br><span class="line"></span><br><span class="line"> @property (nonatomic, strong) NSString * __nonnull icon;</span><br></pre></td></tr></table></figure>
<ul>
<li><p>在<code>NS_ASSUME_NONNULL_BEGIN</code>和<code>NS_ASSUME_NONNULL_END</code>之间,定义的所有对象属性和方法默认都是<code>nonnull</code></p>
</li>
<li><p><code>null_resettable</code>作用: get:不能返回为空, set可以为空</p>
</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">// 书写方式:</span><br><span class="line">@property (nonatomic, strong, null_resettable) NSString *name;</span><br><span class="line"></span><br><span class="line"> // 注意;如果使用null_resettable,必须 重写get方法或者set方法,处理传递的值为空的情况</span><br></pre></td></tr></table></figure>
<ul>
<li><code>_Null_unspecified:</code>不确定是否为空</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">书写方式只有这种</span><br><span class="line"> 方式一</span><br><span class="line"> @property (nonatomic, strong) NSString *_Null_unspecified name;</span><br><span class="line"> 方式二</span><br><span class="line"> @property (nonatomic, strong) NSString *__null_unspecified name;</span><br></pre></td></tr></table></figure>
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<h2 id="Runtime简介"><a href="#Runtime简介" class="headerlink" title="Runtime简介"></a>Runtime简介</h2><ul>
<li>RunTime简称运行时。OC就是<code>运行时机制</code>，也就是在运行时候的一些机制，其中最主要的是消息机制。</li>
<li>对于C语言，<code>函数的调用在编译的时候会决定调用哪个函数。</code><br>对于OC的函数，属于动态调用过程，在编译的时候并不能决定真正调用哪个函数，只有在真正运行的时候才会根据函数的名称找到对应的函数来调用。</li>
<li>事实证明：<ul>
<li>在编译阶段，OC可以<code>调用任何函数</code>，即使这个函数并未实现，只要声明过就不会报错。</li>
<li>在编译阶段，C语言调用<code>未实现的函数</code>就会报错。</li>
</ul>
</li>
</ul>
<h2 id="Runtime作用"><a href="#Runtime作用" class="headerlink" title="Runtime作用"></a>Runtime作用</h2><h3 id="发送消息"><a href="#发送消息" class="headerlink" title="发送消息"></a>发送消息</h3><ul>
<li>方法调用的本质，就是让对象发送消息。</li>
<li>objc_msgSend,只有对象才能发送消息，因此以objc开头.</li>
<li>使用消息机制前提，必须导入#import <objc/message.h></li>
<li>消息机制简单使用</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">// 创建person对象</span><br><span class="line"> Person *p = [[Person alloc] init];</span><br><span class="line"></span><br><span class="line"> // 调用对象方法</span><br><span class="line"> [p eat];</span><br><span class="line"></span><br><span class="line"> // 本质：让对象发送消息</span><br><span class="line"> objc_msgSend(p, @selector(eat));</span><br><span class="line"></span><br><span class="line"> // 调用类方法的方式：两种</span><br><span class="line"> // 第一种通过类名调用</span><br><span class="line"> [Person eat];</span><br><span class="line"> // 第二种通过类对象调用</span><br><span class="line"> [[Person class] eat];</span><br><span class="line"></span><br><span class="line"> // 用类名调用类方法，底层会自动把类名转换成类对象调用</span><br><span class="line"> // 本质：让类对象发送消息</span><br><span class="line"> objc_msgSend([Person class], @selector(eat));</span><br></pre></td></tr></table></figure>
<ul>
<li>消息机制原理:对象根据方法编号SEL去映射表查找对应的方法实现</li>
</ul>
<p><img src="/2019/03/25/runtime学习/Snip20151013_4.png" alt=""></p>
<h3 id="交换方法"><a href="#交换方法" class="headerlink" title="交换方法"></a>交换方法</h3><ul>
<li>开发使用场景:系统自带的方法功能不够，给系统自带的方法扩展一些功能，并且保持原有的功能。</li>
<li>方式一:继承系统的类，重写方法. </li>
<li>方式二:使用runtime,交换方法.</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br></pre></td><td class="code"><pre><span class="line">@implementation ViewController</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">- (void)viewDidLoad {</span><br><span class="line"> [super viewDidLoad];</span><br><span class="line"> // Do any additional setup after loading the view, typically from a nib.</span><br><span class="line"> // 需求：给imageNamed方法提供功能，每次加载图片就判断下图片是否加载成功。</span><br><span class="line"> // 步骤一：先搞个分类，定义一个能加载图片并且能打印的方法+ (instancetype)imageWithName:(NSString *)name;</span><br><span class="line"> // 步骤二：交换imageNamed和imageWithName的实现，就能调用imageWithName，间接调用imageWithName的实现。</span><br><span class="line"> UIImage *image = [UIImage imageNamed:@"123"];</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">@end</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">@implementation UIImage (Image)</span><br><span class="line">// 加载分类到内存的时候调用</span><br><span class="line">+ (void)load</span><br><span class="line">{</span><br><span class="line"> // 交换方法</span><br><span class="line"></span><br><span class="line"> // 获取imageWithName方法地址</span><br><span class="line"> Method imageWithName = class_getClassMethod(self, @selector(imageWithName:));</span><br><span class="line"></span><br><span class="line"> // 获取imageWithName方法地址</span><br><span class="line"> Method imageName = class_getClassMethod(self, @selector(imageNamed:));</span><br><span class="line"></span><br><span class="line"> // 交换方法地址，相当于交换实现方式</span><br><span class="line"> method_exchangeImplementations(imageWithName, imageName);</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">// 不能在分类中重写系统方法imageNamed，因为会把系统的功能给覆盖掉，而且分类中不能调用super.</span><br><span class="line"></span><br><span class="line">// 既能加载图片又能打印</span><br><span class="line">+ (instancetype)imageWithName:(NSString *)name</span><br><span class="line">{</span><br><span class="line"></span><br><span class="line"> // 这里调用imageWithName，相当于调用imageName</span><br><span class="line"> UIImage *image = [self imageWithName:name];</span><br><span class="line"></span><br><span class="line"> if (image == nil) {</span><br><span class="line"> NSLog(@"加载空的图片");</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> return image;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">@end</span><br></pre></td></tr></table></figure>
<ul>
<li>交换原理</li>
</ul>
<p><img src="/2019/03/25/runtime学习/Snip20151013_2.png" alt="交换之前" title="交换之前"></p>
<p><img src="/2019/03/25/runtime学习/Snip20151013_3.png" alt="交换之后" title="交换之后"></p>
<h3 id="动态添加方法"><a href="#动态添加方法" class="headerlink" title="动态添加方法"></a>动态添加方法</h3><ul>
<li>开发使用场景：如果一个类方法非常多，加载类到内存的时候也比较耗费资源，需要给每个方法生成映射表，可以使用动态给某个类，添加方法解决。</li>
<li>经典面试题：有没有使用performSelector，其实主要想问你有没有动态添加过方法。</li>
<li>简单使用</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br></pre></td><td class="code"><pre><span class="line">@implementation ViewController</span><br><span class="line"></span><br><span class="line">- (void)viewDidLoad {</span><br><span class="line"> [super viewDidLoad];</span><br><span class="line"> // Do any additional setup after loading the view, typically from a nib.</span><br><span class="line"></span><br><span class="line"> Person *p = [[Person alloc] init];</span><br><span class="line"></span><br><span class="line"> // 默认person，没有实现eat方法，可以通过performSelector调用，但是会报错。</span><br><span class="line"> // 动态添加方法就不会报错</span><br><span class="line"> [p performSelector:@selector(eat)];</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">@end</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">@implementation Person</span><br><span class="line">// void(*)()</span><br><span class="line">// 默认方法都有两个隐式参数，</span><br><span class="line">void eat(id self,SEL sel)</span><br><span class="line">{</span><br><span class="line"> NSLog(@"%@ %@",self,NSStringFromSelector(sel));</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">// 当一个对象调用未实现的方法，会调用这个方法处理,并且会把对应的方法列表传过来.</span><br><span class="line">// 刚好可以用来判断，未实现的方法是不是我们想要动态添加的方法</span><br><span class="line">+ (BOOL)resolveInstanceMethod:(SEL)sel</span><br><span class="line">{</span><br><span class="line"></span><br><span class="line"> if (sel == @selector(eat)) {</span><br><span class="line"> // 动态添加eat方法</span><br><span class="line"></span><br><span class="line"> // 第一个参数：给哪个类添加方法</span><br><span class="line"> // 第二个参数：添加方法的方法编号</span><br><span class="line"> // 第三个参数：添加方法的函数实现（函数地址）</span><br><span class="line"> // 第四个参数：函数的类型，(返回值+参数类型) v:void @:对象->self :表示SEL->_cmd</span><br><span class="line"> class_addMethod(self, @selector(eat), eat, "v@:");</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> return [super resolveInstanceMethod:sel];</span><br><span class="line">}</span><br><span class="line">@end</span><br></pre></td></tr></table></figure>
<h3 id="给分类添加属性"><a href="#给分类添加属性" class="headerlink" title="给分类添加属性"></a>给分类添加属性</h3><ul>
<li>原理：给一个类声明属性，其实本质就是给这个类添加关联，并不是直接把这个值的内存空间添加到类存空间。</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br></pre></td><td class="code"><pre><span class="line">@implementation ViewController</span><br><span class="line"></span><br><span class="line">- (void)viewDidLoad {</span><br><span class="line"> [super viewDidLoad];</span><br><span class="line"> // Do any additional setup after loading the view, typically from a nib.</span><br><span class="line"></span><br><span class="line"> // 给系统NSObject类动态添加属性name</span><br><span class="line"></span><br><span class="line"> NSObject *objc = [[NSObject alloc] init];</span><br><span class="line"> objc.name = @"小码哥";</span><br><span class="line"> NSLog(@"%@",objc.name);</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">@end</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">// 定义关联的key</span><br><span class="line">static const char *key = "name";</span><br><span class="line"></span><br><span class="line">@implementation NSObject (Property)</span><br><span class="line"></span><br><span class="line">- (NSString *)name</span><br><span class="line">{</span><br><span class="line"> // 根据关联的key，获取关联的值。</span><br><span class="line"> return objc_getAssociatedObject(self, key);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">- (void)setName:(NSString *)name</span><br><span class="line">{</span><br><span class="line"> // 第一个参数：给哪个对象添加关联</span><br><span class="line"> // 第二个参数：关联的key，通过这个key获取</span><br><span class="line"> // 第三个参数：关联的value</span><br><span class="line"> // 第四个参数:关联的策略</span><br><span class="line"> objc_setAssociatedObject(self, key, name, OBJC_ASSOCIATION_RETAIN_NONATOMIC);</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">@end</span><br></pre></td></tr></table></figure>
<h4 id="字典转模型"><a href="#字典转模型" class="headerlink" title="字典转模型"></a>字典转模型</h4><ul>
<li>设计模型：字典转模型的第一步<ul>
<li>模型属性，通常需要跟字典中的key一一对应</li>
<li>问题：一个一个的生成模型属性，很慢？</li>
<li>需求：能不能自动根据一个字典，生成对应的属性。</li>
<li>解决：提供一个分类，专门根据字典生成对应的属性字符串。</li>
</ul>
</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br></pre></td><td class="code"><pre><span class="line"> @implementation NSObject (Log)</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">// 自动打印属性字符串</span><br><span class="line">+ (void)resolveDict:(NSDictionary *)dict{</span><br><span class="line"></span><br><span class="line"> // 拼接属性字符串代码</span><br><span class="line"> NSMutableString *strM = [NSMutableString string];</span><br><span class="line"></span><br><span class="line"> // 1.遍历字典，把字典中的所有key取出来，生成对应的属性代码</span><br><span class="line"> [dict enumerateKeysAndObjectsUsingBlock:^(id _Nonnull key, id _Nonnull obj, BOOL * _Nonnull stop) {</span><br><span class="line"></span><br><span class="line"> // 类型经常变，抽出来</span><br><span class="line"> NSString *type;</span><br><span class="line"></span><br><span class="line"> if ([obj isKindOfClass:NSClassFromString(@"__NSCFString")]) {</span><br><span class="line"> type = @"NSString";</span><br><span class="line"> }else if ([obj isKindOfClass:NSClassFromString(@"__NSCFArray")]){</span><br><span class="line"> type = @"NSArray";</span><br><span class="line"> }else if ([obj isKindOfClass:NSClassFromString(@"__NSCFNumber")]){</span><br><span class="line"> type = @"int";</span><br><span class="line"> }else if ([obj isKindOfClass:NSClassFromString(@"__NSCFDictionary")]){</span><br><span class="line"> type = @"NSDictionary";</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> // 属性字符串</span><br><span class="line"> NSString *str;</span><br><span class="line"> if ([type containsString:@"NS"]) {</span><br><span class="line"> str = [NSString stringWithFormat:@"@property (nonatomic, strong) %@ *%@;",type,key];</span><br><span class="line"> }else{</span><br><span class="line"> str = [NSString stringWithFormat:@"@property (nonatomic, assign) %@ %@;",type,key];</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // 每生成属性字符串，就自动换行。</span><br><span class="line"> [strM appendFormat:@"\n%@\n",str];</span><br><span class="line"></span><br><span class="line"> }];</span><br><span class="line"></span><br><span class="line"> // 把拼接好的字符串打印出来，就好了。</span><br><span class="line"> NSLog(@"%@",strM);</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">@end</span><br></pre></td></tr></table></figure>
<ul>
<li>字典转模型的方式一：KVC</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">@implementation Status</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">+ (instancetype)statusWithDict:(NSDictionary *)dict</span><br><span class="line">{</span><br><span class="line"> Status *status = [[self alloc] init];</span><br><span class="line"></span><br><span class="line"> [status setValuesForKeysWithDictionary:dict];</span><br><span class="line"></span><br><span class="line"> return status;</span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">@end</span><br></pre></td></tr></table></figure>
<ul>
<li>KVC字典转模型弊端：必须保证，模型中的属性和字典中的key一一对应。<ul>
<li>如果不一致，就会调用<code>[<Status 0x7fa74b545d60> setValue:forUndefinedKey:]</code> 报key找不到的错。</li>
<li>分析:模型中的属性和字典的key不一一对应，系统就会调用<code>setValue:forUndefinedKey:</code>报错。</li>
<li>解决:重写对象的<code>setValue:forUndefinedKey:</code>,把系统的方法覆盖， 就能继续使用KVC，字典转模型了。</li>
</ul>
</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">- (void)setValue:(id)value forUndefinedKey:(NSString *)key</span><br><span class="line">{</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<ul>
<li>字典转模型的方式二：Runtime<ul>
<li>思路：利用运行时，遍历模型中所有属性，根据模型的属性名，去字典中查找key，取出对应的值，给模型的属性赋值。</li>
<li>步骤：提供一个NSObject分类，专门字典转模型，以后所有模型都可以通过这个分类转。</li>
</ul>
</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br><span class="line">117</span><br><span class="line">118</span><br><span class="line">119</span><br><span class="line">120</span><br><span class="line">121</span><br><span class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br><span class="line">128</span><br><span class="line">129</span><br><span class="line">130</span><br><span class="line">131</span><br><span class="line">132</span><br><span class="line">133</span><br><span class="line">134</span><br><span class="line">135</span><br><span class="line">136</span><br><span class="line">137</span><br><span class="line">138</span><br><span class="line">139</span><br><span class="line">140</span><br><span class="line">141</span><br><span class="line">142</span><br><span class="line">143</span><br><span class="line">144</span><br><span class="line">145</span><br><span class="line">146</span><br><span class="line">147</span><br><span class="line">148</span><br><span class="line">149</span><br><span class="line">150</span><br><span class="line">151</span><br><span class="line">152</span><br><span class="line">153</span><br><span class="line">154</span><br><span class="line">155</span><br><span class="line">156</span><br><span class="line">157</span><br><span class="line">158</span><br><span class="line">159</span><br><span class="line">160</span><br><span class="line">161</span><br></pre></td><td class="code"><pre><span class="line">@implementation ViewController</span><br><span class="line"></span><br><span class="line">- (void)viewDidLoad {</span><br><span class="line"> [super viewDidLoad];</span><br><span class="line"> // Do any additional setup after loading the view, typically from a nib.</span><br><span class="line"></span><br><span class="line"> // 解析Plist文件</span><br><span class="line"> NSString *filePath = [[NSBundle mainBundle] pathForResource:@"status.plist" ofType:nil];</span><br><span class="line"></span><br><span class="line"> NSDictionary *statusDict = [NSDictionary dictionaryWithContentsOfFile:filePath];</span><br><span class="line"></span><br><span class="line"> // 获取字典数组</span><br><span class="line"> NSArray *dictArr = statusDict[@"statuses"];</span><br><span class="line"></span><br><span class="line"> // 自动生成模型的属性字符串</span><br><span class="line">// [NSObject resolveDict:dictArr[0][@"user"]];</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> _statuses = [NSMutableArray array];</span><br><span class="line"></span><br><span class="line"> // 遍历字典数组</span><br><span class="line"> for (NSDictionary *dict in dictArr) {</span><br><span class="line"></span><br><span class="line"> Status *status = [Status modelWithDict:dict];</span><br><span class="line"></span><br><span class="line"> [_statuses addObject:status];</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // 测试数据</span><br><span class="line"> NSLog(@"%@ %@",_statuses,[_statuses[0] user]);</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">@end</span><br><span class="line"></span><br><span class="line">@implementation NSObject (Model)</span><br><span class="line"></span><br><span class="line">+ (instancetype)modelWithDict:(NSDictionary *)dict</span><br><span class="line">{</span><br><span class="line"> // 思路：遍历模型中所有属性-》使用运行时</span><br><span class="line"></span><br><span class="line"> // 0.创建对应的对象</span><br><span class="line"> id objc = [[self alloc] init];</span><br><span class="line"></span><br><span class="line"> // 1.利用runtime给对象中的成员属性赋值</span><br><span class="line"></span><br><span class="line"> // class_copyIvarList:获取类中的所有成员属性</span><br><span class="line"> // Ivar：成员属性的意思</span><br><span class="line"> // 第一个参数：表示获取哪个类中的成员属性</span><br><span class="line"> // 第二个参数：表示这个类有多少成员属性，传入一个Int变量地址，会自动给这个变量赋值</span><br><span class="line"> // 返回值Ivar *：指的是一个ivar数组，会把所有成员属性放在一个数组中，通过返回的数组就能全部获取到。</span><br><span class="line"> /* 类似下面这种写法</span><br><span class="line"></span><br><span class="line"> Ivar ivar;</span><br><span class="line"> Ivar ivar1;</span><br><span class="line"> Ivar ivar2;</span><br><span class="line"> // 定义一个ivar的数组a</span><br><span class="line"> Ivar a[] = {ivar,ivar1,ivar2};</span><br><span class="line"></span><br><span class="line"> // 用一个Ivar *指针指向数组第一个元素</span><br><span class="line"> Ivar *ivarList = a;</span><br><span class="line"></span><br><span class="line"> // 根据指针访问数组第一个元素</span><br><span class="line"> ivarList[0];</span><br><span class="line"></span><br><span class="line"> */</span><br><span class="line"> unsigned int count;</span><br><span class="line"></span><br><span class="line"> // 获取类中的所有成员属性</span><br><span class="line"> Ivar *ivarList = class_copyIvarList(self, &count);</span><br><span class="line"></span><br><span class="line"> for (int i = 0; i < count; i++) {</span><br><span class="line"> // 根据角标，从数组取出对应的成员属性</span><br><span class="line"> Ivar ivar = ivarList[i];</span><br><span class="line"></span><br><span class="line"> // 获取成员属性名</span><br><span class="line"> NSString *name = [NSString stringWithUTF8String:ivar_getName(ivar)];</span><br><span class="line"></span><br><span class="line"> // 处理成员属性名->字典中的key</span><br><span class="line"> // 从第一个角标开始截取</span><br><span class="line"> NSString *key = [name substringFromIndex:1];</span><br><span class="line"></span><br><span class="line"> // 根据成员属性名去字典中查找对应的value</span><br><span class="line"> id value = dict[key];</span><br><span class="line"></span><br><span class="line"> // 二级转换:如果字典中还有字典，也需要把对应的字典转换成模型</span><br><span class="line"> // 判断下value是否是字典</span><br><span class="line"> if ([value isKindOfClass:[NSDictionary class]]) {</span><br><span class="line"> // 字典转模型</span><br><span class="line"> // 获取模型的类对象，调用modelWithDict</span><br><span class="line"> // 模型的类名已知，就是成员属性的类型</span><br><span class="line"></span><br><span class="line"> // 获取成员属性类型</span><br><span class="line"> NSString *type = [NSString stringWithUTF8String:ivar_getTypeEncoding(ivar)];</span><br><span class="line"> // 生成的是这种@"@\"User\"" 类型 -》 @"User" 在OC字符串中 \" -> "，\是转义的意思，不占用字符</span><br><span class="line"> // 裁剪类型字符串</span><br><span class="line"> NSRange range = [type rangeOfString:@"\""];</span><br><span class="line"></span><br><span class="line"> type = [type substringFromIndex:range.location + range.length];</span><br><span class="line"></span><br><span class="line"> range = [type rangeOfString:@"\""];</span><br><span class="line"></span><br><span class="line"> // 裁剪到哪个角标，不包括当前角标</span><br><span class="line"> type = [type substringToIndex:range.location];</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> // 根据字符串类名生成类对象</span><br><span class="line"> Class modelClass = NSClassFromString(type);</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> if (modelClass) { // 有对应的模型才需要转</span><br><span class="line"></span><br><span class="line"> // 把字典转模型</span><br><span class="line"> value = [modelClass modelWithDict:value];</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // 三级转换：NSArray中也是字典，把数组中的字典转换成模型.</span><br><span class="line"> // 判断值是否是数组</span><br><span class="line"> if ([value isKindOfClass:[NSArray class]]) {</span><br><span class="line"> // 判断对应类有没有实现字典数组转模型数组的协议</span><br><span class="line"> if ([self respondsToSelector:@selector(arrayContainModelClass)]) {</span><br><span class="line"></span><br><span class="line"> // 转换成id类型，就能调用任何对象的方法</span><br><span class="line"> id idSelf = self;</span><br><span class="line"></span><br><span class="line"> // 获取数组中字典对应的模型</span><br><span class="line"> NSString *type = [idSelf arrayContainModelClass][key];</span><br><span class="line"></span><br><span class="line"> // 生成模型</span><br><span class="line"> Class classModel = NSClassFromString(type);</span><br><span class="line"> NSMutableArray *arrM = [NSMutableArray array];</span><br><span class="line"> // 遍历字典数组，生成模型数组</span><br><span class="line"> for (NSDictionary *dict in value) {</span><br><span class="line"> // 字典转模型</span><br><span class="line"> id model = [classModel modelWithDict:dict];</span><br><span class="line"> [arrM addObject:model];</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> // 把模型数组赋值给value</span><br><span class="line"> value = arrM;</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> if (value) { // 有值，才需要给模型的属性赋值</span><br><span class="line"> // 利用KVC给模型中的属性赋值</span><br><span class="line"> [objc setValue:value forKey:key];</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> return objc;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">@end</span><br></pre></td></tr></table></figure>
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<p>新年新计划</p>
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<h3 id="iOS大牛技术博客收藏贴"><a href="#iOS大牛技术博客收藏贴" class="headerlink" title="iOS大牛技术博客收藏贴"></a>iOS大牛技术博客收藏贴</h3><ul>
<li><p><a href="http://www.tanhao.me/" target="_blank" rel="noopener">谭灏的博客：目前就职于腾讯mac管家部门，他是一名 OSX、iOS 程序员，他的博客中有许多mac，ios开发的文章，值得大家去品读</a></p>
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<li><p><a href="https://www.jianshu.com/u/b82d2721ba07" target="_blank" rel="noopener">叶孤城的博客：就职于百度</a></p>
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<li><p><a href="http://southpeak.github.io/" target="_blank" rel="noopener">南峰子的博客：就职于百度</a></p>
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<li><p><a href="http://nianxi.net" target="_blank" rel="noopener">吴茜的博客：目前就职阿里旗下蚂蚁金服</a></p>
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<li><p><a href="https://github.com/ChenYilong" target="_blank" rel="noopener">ChenYilong的Github：曾就职于leancloud，现就职于猿题库</a></p>
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<li><p><a href="http://gracelancy.com/" target="_blank" rel="noopener">晨钰Lancy 猿题库 iOS 研发工程师</a></p>