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Diffstat (limited to '2024/05/03')
| -rw-r--r-- | 2024/05/03/Rust-NewType-模式/index.html | 283 |
1 files changed, 0 insertions, 283 deletions
diff --git a/2024/05/03/Rust-NewType-模式/index.html b/2024/05/03/Rust-NewType-模式/index.html deleted file mode 100644 index 17ca00b2..00000000 --- a/2024/05/03/Rust-NewType-模式/index.html +++ /dev/null @@ -1,283 +0,0 @@ -<!DOCTYPE html> -<html lang="en"> - <head> - <meta charset="UTF-8"> -<meta name="viewport" - content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0"> -<meta http-equiv="X-UA-Compatible" content="ie=edge"> - - <meta name="author" content="韩暮秋"> - - - <meta name="subtitle" content="暮秋小屋"> - - - <meta name="description" content="这里是暮秋小屋，思念和灵感的寄存处"> - - - <meta name="keywords" content="韩暮秋,MuqiuHan,'Muqiu Han', 'muqiu han', muqiuhan"> - - - - -<title>Rust NewType 模式 | 暮秋小屋</title> - - - - <link rel="icon" href="/favicon.ico"> - - - -<style> - @import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Noto+Sans+SC:wght@300;400;500;700&family=Roboto+Mono&display=swap'); -</style> - - - - <!-- stylesheets list from _config.yml --> - - <link rel="stylesheet" href="/css/style.css"> - - - - - - <!-- scripts list from _config.yml --> - - <script src="/js/frame.js"></script> - - - - - - <script src="https://polyfill.io/v3/polyfill.min.js?features=es6"></script> - <script id="MathJax-script" async src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script> - - - - - - - - <meta name="generator" content="Hexo 6.3.0"></head> - <body> - <div class="mask-border"> - </div> - - <div class="wrapper"> - - <div class="header"> - <div class="flex-container"> - <div class="header-inner"> - <div class="site-brand-container"> - <a href="/"> - - 暮秋小屋 - - </a> - </div> - <div id="menu-btn" class="menu-btn" onclick="toggleMenu()"> - Menu - </div> - <nav class="site-nav"> - <ul class="menu-list"> - - - <li class="menu-item"> - <a href="/">主页</a> - </li> - - - - <li class="menu-item"> - <a href="/categories/gallery/">日记本</a> - </li> - - - - <li class="menu-item"> - <a href="/tags/Medicine/">医学</a> - </li> - - - - <li class="menu-item"> - <a href="/tags/Technique/">计算机科学</a> - </li> - - - - <li class="menu-item"> - <a href="/tags/Life/">生活</a> - </li> - - - - <li class="menu-item"> - <a href="/about">关于</a> - </li> - - - - <li class="menu-item search-btn"> - <a href="#">Search</a> - </li> - - </ul> - </nav> - </div> - </div> -</div> - - - <div class="main"> - <div class="flex-container"> - <article id="post"> - - - <div class="post-head"> - <div class="post-info"> - <div class="tag-list"> - - - <span class="post-tag"> - <a href="/tags/Technique/"> - Technique - </a> - </span> - - <span class="post-tag"> - <a href="/tags/Rust/"> - Rust - </a> - </span> - - - </div> - <div class="post-title"> - - - Rust NewType 模式 - - - </div> - <span class="post-date"> - May 3, 2024 - </span> - </div> - <div class="post-img"> - - <div class="h-line-primary"></div> - - </div> -</div> - <div class="post-content"> - <p>New Type模式是一种软件设计模式，用于在已有类型的基础上创建一个新的类型。在Rust中，这通常是通过<strong>定义一个结构体，其中只包含一个单一成员。这个结构体（New Type）对外提供了一个新的、独立的类型，用于对原始类型增加额外的语义或限制。</strong></p> -<h2 id="加强类型安全"><a href="#加强类型安全" class="headerlink" title="加强类型安全"></a>加强类型安全</h2><figure class="highlight rust"><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></pre></td><td class="code"><pre><span class="line"><span class="keyword">struct</span> <span class="title class_">Meters</span>(<span class="type">f64</span>);</span><br><span class="line"><span class="keyword">struct</span> <span class="title class_">Feet</span>(<span class="type">f64</span>);</span><br><span class="line"></span><br><span class="line"><span class="keyword">let</span> <span class="variable">length_in_meters</span> = <span class="title function_ invoke__">Meters</span>(<span class="number">100.0</span>);</span><br><span class="line"><span class="keyword">let</span> <span class="variable">length_in_feet</span> = <span class="title function_ invoke__">Feet</span>(<span class="number">328.084</span>);</span><br><span class="line"></span><br><span class="line"><span class="comment">// 编译器会防止以下代码执行，因为类型不匹配</span></span><br><span class="line"><span class="comment">// let wrong_length = Meters(length_in_feet); // 编译错误</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 正确的构造</span></span><br><span class="line"><span class="keyword">fn</span> <span class="title function_">add_lengths</span>(length1: Meters, length2: Meters) <span class="punctuation">-></span> Meters {</span><br><span class="line"> <span class="title function_ invoke__">Meters</span>(length1.<span class="number">0</span> + length2.<span class="number">0</span>)</span><br><span class="line">}</span><br></pre></td></tr></table></figure> - -<p>这个例子使用 newtype 模式避免将原始类型f64用于不同的量度，从而增强了类型的安全性。</p> -<h2 id="实现特定-trait"><a href="#实现特定-trait" class="headerlink" title="实现特定 trait"></a>实现特定 trait</h2><figure class="highlight rust"><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></pre></td><td class="code"><pre><span class="line"><span class="keyword">struct</span> <span class="title class_">Kilometers</span>(<span class="type">f64</span>);</span><br><span class="line"></span><br><span class="line"><span class="keyword">impl</span> <span class="title class_">Kilometers</span> {</span><br><span class="line"> <span class="keyword">fn</span> <span class="title function_">to_miles</span>(&<span class="keyword">self</span>) <span class="punctuation">-></span> <span class="type">f64</span> {</span><br><span class="line"> <span class="keyword">self</span>.<span class="number">0</span> * <span class="number">0.621371</span></span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">let</span> <span class="variable">distance</span> = <span class="title function_ invoke__">Kilometers</span>(<span class="number">10.0</span>);</span><br><span class="line"><span class="built_in">println!</span>(<span class="string">"The distance in miles is {}"</span>, distance.<span class="title function_ invoke__">to_miles</span>());</span><br></pre></td></tr></table></figure> - -<p>这里，Kilometers有一个方法to_miles，该方法是不会影响其他f64数据的。如果我们有另一个表示温度的f64类型，就不会意外调用到与距离相关的方法。</p> -<p>New Type模式同样适用于对<code>Box<dyn SomeTrait></code>类型的包装，这可以在需要动态分派（动态调用实现了某个接口的不同类型的对象的方法）的时候提供便利。通过创建一个New Type来包装这样的<code>Box<dyn SomeTrait></code>类型，可以提供自定义的方法或实现更多的trait，同时也可以让API更加清晰和易于使用。</p> -<h2 id="零成本抽象"><a href="#零成本抽象" class="headerlink" title="零成本抽象"></a>零成本抽象</h2><p>在Rust中，New Type模式不仅是类型安全的，还是一种零成本抽象。这是因为Rust编译器在编译时期会进行足够的优化，以确保New Type的使用没有运行时开销。 Rust的零成本抽象原则确保了抽象不会引入额外的运行时成本。例如，当你使用Meters这样的New Type时，Rust确保：</p> -<ol> -<li>无额外内存开销：Meters只包含一个f64，在内存中的表现和单独的f64是一样的。</li> -<li>无额外运行时开销：使用Meters时，性能和直接使用f64完全相同。编译器会移除任何关于New Type的包装和解包的代码。</li> -</ol> - -</div> - -<script> - window.onload = detectors(); 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