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Diffstat (limited to '2023/05/24/Rust-闭包-lifetime-may-not-live-long-enough-问题/index.html')
| -rw-r--r-- | 2023/05/24/Rust-闭包-lifetime-may-not-live-long-enough-问题/index.html | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/2023/05/24/Rust-闭包-lifetime-may-not-live-long-enough-问题/index.html b/2023/05/24/Rust-闭包-lifetime-may-not-live-long-enough-问题/index.html index e208733c..a44f767e 100644 --- a/2023/05/24/Rust-闭包-lifetime-may-not-live-long-enough-问题/index.html +++ b/2023/05/24/Rust-闭包-lifetime-may-not-live-long-enough-问题/index.html @@ -194,13 +194,12 @@ <div class="post-content"> <p>代码：</p> <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><br><span class="line"> <span class="keyword">fn</span> <span class="title function_">handlers</span>(<span class="keyword">self</span>) <span class="punctuation">-></span> crate::server::request::Handlers {</span><br><span class="line"> <span class="built_in">vec!</span>[(</span><br><span class="line"> <span class="string">"/tree"</span>,</span><br><span class="line"> routing::<span class="title function_ invoke__">get</span>(<span class="keyword">move</span> || <span class="keyword">async</span> {</span><br><span class="line"> (</span><br><span class="line"> StatusCode::OK,</span><br><span class="line"> <span class="title function_ invoke__">Json</span>(json!(<span class="keyword">self</span>.<span class="title function_ invoke__">clone</span>().<span class="title function_ invoke__">tree</span>(<span class="keyword">self</span>.<span class="title function_ invoke__">clone</span>().root))),</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></pre></td></tr></table></figure> - <p>编译错误：</p> <figure class="highlight text"><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></pre></td><td class="code"><pre><span class="line">error: lifetime may not live long enough</span><br><span class="line"> --> src/storage/filesystem/mod.rs:45:34</span><br><span class="line"> |</span><br><span class="line">45 | routing::get(move || async {</span><br><span class="line"> | __________________________-------_^</span><br><span class="line"> | | | |</span><br><span class="line"> | | | return type of closure `{async block@src/storage/filesystem/mod.rs:45:34: 50:14}` contains a lifetime `'2`</span><br><span class="line"> | | lifetime `'1` represents this closure's body</span><br><span class="line">46 | | (</span><br><span class="line">47 | | StatusCode::OK,</span><br><span class="line">48 | | Json(json!(self.clone().tree(self.clone().root))),</span><br><span class="line">49 | | )</span><br><span class="line">50 | | }),</span><br><span class="line"> | |_____________^ returning this value requires that `'1` must outlive `'2`</span><br><span class="line"> |</span><br><span class="line"> = note: closure implements `Fn`, so references to captured variables can't escape the closure</span><br></pre></td></tr></table></figure> - <p>这是因为 <code>handlers</code> 里面的闭包捕获了一个引用，并且尝试返回一个包含该引用的值导致的。</p> <p>细说就是：闭包内部使用了 <code>self.clone()</code> 来获取一个新的实例，然后在异步块中返回一个 JSON 对象，这个 JSON 对象依赖于 <code>self.tree()</code> 的结果。因为闭包捕获了 <code>self</code> 的引用，所以它必须保证 <code>self</code> 在闭包执行完毕后仍然有效。</p> -<p>解决这个问题的思路是：确保闭包中的所有引用都在闭包执行完毕之前就不再被使用。<br>就是说，要将闭包的作用域限制在一个更短的生命周期内，或者使用其他方式来避免闭包捕获长期存在的引用:</p> +<p>解决这个问题的思路是：确保闭包中的所有引用都在闭包执行完毕之前就不再被使用。<br> +就是说，要将闭包的作用域限制在一个更短的生命周期内，或者使用其他方式来避免闭包捕获长期存在的引用:</p> <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><br><span class="line">...</span><br><span class="line"> <span class="keyword">fn</span> <span class="title function_">handlers</span>(<span class="keyword">self</span>) <span class="punctuation">-></span> crate::server::request::Handlers {</span><br><span class="line"> <span class="keyword">let</span> <span class="variable">tree</span> = json!(<span class="keyword">self</span>.<span class="title function_ invoke__">clone</span>().<span class="title function_ invoke__">tree</span>(<span class="keyword">self</span>.<span class="title function_ invoke__">clone</span>().root));</span><br><span class="line"> <span class="built_in">vec!</span>[(</span><br><span class="line"> <span class="string">"/tree"</span>,</span><br><span class="line"> routing::<span class="title function_ invoke__">get</span>(<span class="keyword">move</span> || <span class="keyword">async</span> { (StatusCode::OK, <span class="title function_ invoke__">Json</span>(tree)) }),</span><br><span class="line"> )]</span><br><span class="line"> }</span><br><span class="line">...</span><br></pre></td></tr></table></figure> </div> |