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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<title>Better Method Chaining in Rust</title>
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</head>
<body>
<div class="reveal">
<div class="slides">
<section>
<h1>Discussion: Better Method Chaining in Rust</h1>
</section>
<section>
<h2>A Real-World Example</h2>
<section>
<pre><code class="rust" data-trim>
let result = Command::new("foo")
.arg("--bar")
.arg("--baz")
.arg("quux")
.status()
.unwrap();
</code></pre>
</section>
<section>
<pre><code class="rust" data-trim>
let command = Command::new("foo")
.arg("--bar");
if set_baz {
command.arg("--baz");
}
let result = command
.arg("quux")
.status()
.unwrap();
</code></pre>
</section>
<section>
<pre><code class="rust" data-trim>
error[E0716]: temporary value dropped while borrowed
--> src/main.rs:6:19
|
6 | let command = Command::new("foo").arg("--bar");
| ^^^^^^^^^^^^^^^^^^^ - temporary value is freed at the end of this statement
| |
| creates a temporary which is freed while still in use
...
9 | command.arg("--baz");
| ------- borrow later used here
|
= note: consider using a `let` binding to create a longer lived value
</code></pre>
</section>
<section>
<pre><code class="rust" data-trim data-noescape>
<mark>let mut command = Command::new("foo");</mark>
command.arg("--bar");
if set_baz {
command.arg("--baz");
}
let result = command
.arg("quux")
.status()
.unwrap();
</code></pre>
</section>
</section>
<section>
<h2>Method Chaining Today</h2>
<section>
<pre><code class="rust" data-trim>
pub fn arg<S>(&mut self, arg: S) -> &mut Command {
// Add the argument...
self
}
</code></pre>
</section>
<section>
<pre><code class="rust" data-trim>
pub fn chain_ref(&mut self) -> &mut Self {
// Do some work...
self
}
pub fn chain_move(mut self) -> Self {
// Do some work...
self
}
</code></pre>
</section>
</section>
<section data-markdown>
<textarea data-template>
From [Chaining Functions Without Returning Self](https://randompoison.github.io/posts/returning-self/):
> The fundamental problem with returning `self`... is that you’re
> contorting your API in order to enable something that’s completely
> orthogonal to what your API is doing. Your function’s signature
> should reflect its behavior, and should be usable in a method
> chain regardless of its return type.
</textarea>
</section>
<section>
<h2>A Digression</h2>
<section data-markdown>
<textarea data-template>
```rust
foo().bar().baz();
```
vs
```rust
baz(bar(foo()))
```
</textarea>
</section>
<section data-markdown>
<textarea data-template>
"cascade" vs "pipeline"
</textarea>
</section>
<section>
<pre><code class="dart" data-trim>
someValue
..foo()
..bar()
..baz();
</code></pre>
</section>
<section>
<pre><code class="elixir" data-trim>
foo() |> bar() |> baz()
</code></pre>
</section>
</section>
<section>
<section>
<h2>Some Existing Alternatives</h2>
</section>
<section>
<h3>cascade</h3>
<pre><code class="rust" data-trim>
let cascaded_list = cascade! {
Vec::new();
..push("Cascades");
..push("reduce");
..push("boilerplate");
};
</code></pre>
</section>
<section>
<h3>pipeline</h3>
<pre><code class="rust" data-trim>
let result = pipe_res!(
"http://rust-lang.org"
=> download
=> parse
=> get_links
);
</code></pre>
</section>
</section>
<section>
<h2>Discuss!</h2>
</section>
</div>
</div>
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