rust
/
rust-course
mirror of https://github.com/sunface/rust-course
5
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
Branches Tags
${ item.name }
Create tag ${ searchTerm }
Create branch ${ searchTerm }
from 'dbbf4037ca'
${ noResults }
rust-course/advance/errors.html

818 lines
86 KiB
Raw Blame History Escape

This file contains ambiguous Unicode characters!

This file contains ambiguous Unicode characters that may be confused with others in your current locale. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to highlight these characters.

<!DOCTYPE HTML>
<html lang="zh-CN" class="light" dir="ltr">
<head>
<!-- Book generated using mdBook -->
<meta charset="UTF-8">
<title>错误处理 - Rust语言圣经(Rust Course)</title>
<!-- Custom HTML head -->
<meta name="description" content="">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="theme-color" content="#ffffff">
<link rel="icon" href="../favicon.svg">
<link rel="shortcut icon" href="../favicon.png">
<link rel="stylesheet" href="../css/variables.css">
<link rel="stylesheet" href="../css/general.css">
<link rel="stylesheet" href="../css/chrome.css">
<link rel="stylesheet" href="../css/print.css" media="print">
<!-- Fonts -->
<link rel="stylesheet" href="../FontAwesome/css/font-awesome.css">
<link rel="stylesheet" href="../fonts/fonts.css">
<!-- Highlight.js Stylesheets -->
<link rel="stylesheet" href="../highlight.css">
<link rel="stylesheet" href="../tomorrow-night.css">
<link rel="stylesheet" href="../ayu-highlight.css">
<!-- Custom theme stylesheets -->
<link rel="stylesheet" href="../theme/style.css">
</head>
<body class="sidebar-visible no-js">
<div id="body-container">
<!-- Provide site root to javascript -->
<script>
var path_to_root = "../";
var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "navy" : "light";
</script>
<!-- Work around some values being stored in localStorage wrapped in quotes -->
<script>
try {
var theme = localStorage.getItem('mdbook-theme');
var sidebar = localStorage.getItem('mdbook-sidebar');
if (theme.startsWith('"') && theme.endsWith('"')) {
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
}
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
}
} catch (e) { }
</script>
<!-- Set the theme before any content is loaded, prevents flash -->
<script>
var theme;
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
if (theme === null || theme === undefined) { theme = default_theme; }
var html = document.querySelector('html');
html.classList.remove('light')
html.classList.add(theme);
var body = document.querySelector('body');
body.classList.remove('no-js')
body.classList.add('js');
</script>
<input type="checkbox" id="sidebar-toggle-anchor" class="hidden">
<!-- Hide / unhide sidebar before it is displayed -->
<script>
var body = document.querySelector('body');
var sidebar = null;
var sidebar_toggle = document.getElementById("sidebar-toggle-anchor");
if (document.body.clientWidth >= 1080) {
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
sidebar = sidebar || 'visible';
} else {
sidebar = 'hidden';
}
sidebar_toggle.checked = sidebar === 'visible';
body.classList.remove('sidebar-visible');
body.classList.add("sidebar-" + sidebar);
</script>
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
<div class="sidebar-scrollbox">
<ol class="chapter"><li class="chapter-item affix "><a href="../about-book.html">关于本书</a></li><li class="chapter-item affix "><a href="../into-rust.html">进入 Rust 编程世界</a></li><li class="chapter-item affix "><a href="../first-try/sth-you-should-not-do.html">避免从入门到放弃</a></li><li class="chapter-item affix "><a href="../community.html">社区和锈书</a></li><li class="spacer"></li><li class="chapter-item affix "><a href="../some-thoughts.html">Datav: 可编程的数据可视化平台和可观测性平台</a></li><li class="chapter-item affix "><li class="part-title">Rust 语言基础学习</li><li class="spacer"></li><li class="chapter-item "><a href="../first-try/intro.html"><strong aria-hidden="true">1.</strong> 寻找牛刀，以便小试</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../first-try/installation.html"><strong aria-hidden="true">1.1.</strong> 安装 Rust 环境</a></li><li class="chapter-item "><a href="../first-try/editor.html"><strong aria-hidden="true">1.2.</strong> 墙推 VSCode!</a></li><li class="chapter-item "><a href="../first-try/cargo.html"><strong aria-hidden="true">1.3.</strong> 认识 Cargo</a></li><li class="chapter-item "><a href="../first-try/hello-world.html"><strong aria-hidden="true">1.4.</strong> 不仅仅是 Hello world</a></li><li class="chapter-item "><a href="../first-try/slowly-downloading.html"><strong aria-hidden="true">1.5.</strong> 下载依赖太慢了？</a></li></ol></li><li class="chapter-item "><a href="../basic/intro.html"><strong aria-hidden="true">2.</strong> Rust 基础入门</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/variable.html"><strong aria-hidden="true">2.1.</strong> 变量绑定与解构</a></li><li class="chapter-item "><a href="../basic/base-type/index.html"><strong aria-hidden="true">2.2.</strong> 基本类型</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/base-type/numbers.html"><strong aria-hidden="true">2.2.1.</strong> 数值类型</a></li><li class="chapter-item "><a href="../basic/base-type/char-bool.html"><strong aria-hidden="true">2.2.2.</strong> 字符、布尔、单元类型</a></li><li class="chapter-item "><a href="../basic/base-type/statement-expression.html"><strong aria-hidden="true">2.2.3.</strong> 语句与表达式</a></li><li class="chapter-item "><a href="../basic/base-type/function.html"><strong aria-hidden="true">2.2.4.</strong> 函数</a></li></ol></li><li class="chapter-item "><a href="../basic/ownership/index.html"><strong aria-hidden="true">2.3.</strong> 所有权和借用</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/ownership/ownership.html"><strong aria-hidden="true">2.3.1.</strong> 所有权</a></li><li class="chapter-item "><a href="../basic/ownership/borrowing.html"><strong aria-hidden="true">2.3.2.</strong> 引用与借用</a></li></ol></li><li class="chapter-item "><a href="../basic/compound-type/intro.html"><strong aria-hidden="true">2.4.</strong> 复合类型</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/compound-type/string-slice.html"><strong aria-hidden="true">2.4.1.</strong> 字符串与切片</a></li><li class="chapter-item "><a href="../basic/compound-type/tuple.html"><strong aria-hidden="true">2.4.2.</strong> 元组</a></li><li class="chapter-item "><a href="../basic/compound-type/struct.html"><strong aria-hidden="true">2.4.3.</strong> 结构体</a></li><li class="chapter-item "><a href="../basic/compound-type/enum.html"><strong aria-hidden="true">2.4.4.</strong> 枚举</a></li><li class="chapter-item "><a href="../basic/compound-type/array.html"><strong aria-hidden="true">2.4.5.</strong> 数组</a></li></ol></li><li class="chapter-item "><a href="../basic/flow-control.html"><strong aria-hidden="true">2.5.</strong> 流程控制</a></li><li class="chapter-item "><a href="../basic/match-pattern/intro.html"><strong aria-hidden="true">2.6.</strong> 模式匹配</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/match-pattern/match-if-let.html"><strong aria-hidden="true">2.6.1.</strong> match 和 if let</a></li><li class="chapter-item "><a href="../basic/match-pattern/option.html"><strong aria-hidden="true">2.6.2.</strong> 解构 Option</a></li><li class="chapter-item "><a href="../basic/match-pattern/pattern-match.html"><strong aria-hidden="true">2.6.3.</strong> 模式适用场景</a></li><li class="chapter-item "><a href="../basic/match-pattern/all-patterns.html"><strong aria-hidden="true">2.6.4.</strong> 全模式列表</a></li></ol></li><li class="chapter-item "><a href="../basic/method.html"><strong aria-hidden="true">2.7.</strong> 方法 Method</a></li><li class="chapter-item "><a href="../basic/trait/intro.html"><strong aria-hidden="true">2.8.</strong> 泛型和特征</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/trait/generic.html"><strong aria-hidden="true">2.8.1.</strong> 泛型 Generics</a></li><li class="chapter-item "><a href="../basic/trait/trait.html"><strong aria-hidden="true">2.8.2.</strong> 特征 Trait</a></li><li class="chapter-item "><a href="../basic/trait/trait-object.html"><strong aria-hidden="true">2.8.3.</strong> 特征对象</a></li><li class="chapter-item "><a href="../basic/trait/advance-trait.html"><strong aria-hidden="true">2.8.4.</strong> 进一步深入特征</a></li></ol></li><li class="chapter-item "><a href="../basic/collections/intro.html"><strong aria-hidden="true">2.9.</strong> 集合类型</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/collections/vector.html"><strong aria-hidden="true">2.9.1.</strong> 动态数组 Vector</a></li><li class="chapter-item "><a href="../basic/collections/hashmap.html"><strong aria-hidden="true">2.9.2.</strong> KV 存储 HashMap</a></li></ol></li><li class="chapter-item "><a href="../basic/lifetime.html"><strong aria-hidden="true">2.10.</strong> 认识生命周期</a></li><li class="chapter-item "><a href="../basic/result-error/intro.html"><strong aria-hidden="true">2.11.</strong> 返回值和错误处理</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/result-error/panic.html"><strong aria-hidden="true">2.11.1.</strong> panic! 深入剖析</a></li><li class="chapter-item "><a href="../basic/result-error/result.html"><strong aria-hidden="true">2.11.2.</strong> 返回值 Result 和?</a></li></ol></li><li class="chapter-item "><a href="../basic/crate-module/intro.html"><strong aria-hidden="true">2.12.</strong> 包和模块</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic/crate-module/crate.html"><strong aria-hidden="true">2.12.1.</strong> 包 Crate</a></li><li class="chapter-item "><a href="../basic/crate-module/module.html"><strong aria-hidden="true">2.12.2.</strong> 模块 Module</a></li><li class="chapter-item "><a href="../basic/crate-module/use.html"><strong aria-hidden="true">2.12.3.</strong> 使用 use 引入模块及受限可见性</a></li></ol></li><li class="chapter-item "><a href="../basic/comment.html"><strong aria-hidden="true">2.13.</strong> 注释和文档</a></li><li class="chapter-item "><a href="../basic/formatted-output.html"><strong aria-hidden="true">2.14.</strong> 格式化输出</a></li></ol></li><li class="chapter-item "><a href="../basic-practice/intro.html"><strong aria-hidden="true">3.</strong> 入门实战：文件搜索工具</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../basic-practice/base-features.html"><strong aria-hidden="true">3.1.</strong> 基本功能</a></li><li class="chapter-item "><a href="../basic-practice/refactoring.html"><strong aria-hidden="true">3.2.</strong> 增加模块化和错误处理</a></li><li class="chapter-item "><a href="../basic-practice/tests.html"><strong aria-hidden="true">3.3.</strong> 测试驱动开发</a></li><li class="chapter-item "><a href="../basic-practice/envs.html"><strong aria-hidden="true">3.4.</strong> 使用环境变量</a></li><li class="chapter-item "><a href="../basic-practice/stderr.html"><strong aria-hidden="true">3.5.</strong> 重定向错误信息的输出</a></li><li class="chapter-item "><a href="../basic-practice/iterators.html"><strong aria-hidden="true">3.6.</strong> 使用迭代器来改进程序(可选)</a></li></ol></li><li class="chapter-item "><li class="part-title">Rust 语言进阶学习</li><li class="spacer"></li><li class="chapter-item expanded "><a href="../advance/intro.html"><strong aria-hidden="true">4.</strong> Rust 高级进阶</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/lifetime/intro.html"><strong aria-hidden="true">4.1.</strong> 生命周期</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/lifetime/advance.html"><strong aria-hidden="true">4.1.1.</strong> 深入生命周期</a></li><li class="chapter-item "><a href="../advance/lifetime/static.html"><strong aria-hidden="true">4.1.2.</strong> &'static 和 T: 'static</a></li></ol></li><li class="chapter-item "><a href="../advance/functional-programing/intro.html"><strong aria-hidden="true">4.2.</strong> 函数式编程: 闭包、迭代器</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/functional-programing/closure.html"><strong aria-hidden="true">4.2.1.</strong> 闭包 Closure</a></li><li class="chapter-item "><a href="../advance/functional-programing/iterator.html"><strong aria-hidden="true">4.2.2.</strong> 迭代器 Iterator</a></li></ol></li><li class="chapter-item "><a href="../advance/into-types/intro.html"><strong aria-hidden="true">4.3.</strong> 深入类型</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/into-types/converse.html"><strong aria-hidden="true">4.3.1.</strong> 类型转换</a></li><li class="chapter-item "><a href="../advance/into-types/custom-type.html"><strong aria-hidden="true">4.3.2.</strong> newtype 和 类型别名</a></li><li class="chapter-item "><a href="../advance/into-types/sized.html"><strong aria-hidden="true">4.3.3.</strong> Sized 和不定长类型 DST</a></li><li class="chapter-item "><a href="../advance/into-types/enum-int.html"><strong aria-hidden="true">4.3.4.</strong> 枚举和整数</a></li></ol></li><li class="chapter-item "><a href="../advance/smart-pointer/intro.html"><strong aria-hidden="true">4.4.</strong> 智能指针</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/smart-pointer/box.html"><strong aria-hidden="true">4.4.1.</strong> Box堆对象分配</a></li><li class="chapter-item "><a href="../advance/smart-pointer/deref.html"><strong aria-hidden="true">4.4.2.</strong> Deref 解引用</a></li><li class="chapter-item "><a href="../advance/smart-pointer/drop.html"><strong aria-hidden="true">4.4.3.</strong> Drop 释放资源</a></li><li class="chapter-item "><a href="../advance/smart-pointer/rc-arc.html"><strong aria-hidden="true">4.4.4.</strong> Rc 与 Arc 实现 1vN 所有权机制</a></li><li class="chapter-item "><a href="../advance/smart-pointer/cell-refcell.html"><strong aria-hidden="true">4.4.5.</strong> Cell 与 RefCell 内部可变性</a></li></ol></li><li class="chapter-item "><a href="../advance/circle-self-ref/intro.html"><strong aria-hidden="true">4.5.</strong> 循环引用与自引用</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/circle-self-ref/circle-reference.html"><strong aria-hidden="true">4.5.1.</strong> Weak 与循环引用</a></li><li class="chapter-item "><a href="../advance/circle-self-ref/self-referential.html"><strong aria-hidden="true">4.5.2.</strong> 结构体中的自引用</a></li></ol></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/intro.html"><strong aria-hidden="true">4.6.</strong> 多线程并发编程</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/concurrency-with-threads/concurrency-parallelism.html"><strong aria-hidden="true">4.6.1.</strong> 并发和并行</a></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/thread.html"><strong aria-hidden="true">4.6.2.</strong> 使用多线程</a></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/message-passing.html"><strong aria-hidden="true">4.6.3.</strong> 线程同步：消息传递</a></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/sync1.html"><strong aria-hidden="true">4.6.4.</strong> 线程同步：锁、Condvar 和信号量</a></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/sync2.html"><strong aria-hidden="true">4.6.5.</strong> 线程同步：Atomic 原子操作与内存顺序</a></li><li class="chapter-item "><a href="../advance/concurrency-with-threads/send-sync.html"><strong aria-hidden="true">4.6.6.</strong> 基于 Send 和 Sync 的线程安全</a></li></ol></li><li class="chapter-item "><a href="../advance/global-variable.html"><strong aria-hidden="true">4.7.</strong> 全局变量</a></li><li class="chapter-item expanded "><a href="../advance/errors.html" class="active"><strong aria-hidden="true">4.8.</strong> 错误处理</a></li><li class="chapter-item "><a href="../advance/unsafe/intro.html"><strong aria-hidden="true">4.9.</strong> Unsafe Rust</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/unsafe/superpowers.html"><strong aria-hidden="true">4.9.1.</strong> 五种兵器</a></li><li class="chapter-item "><a href="../advance/unsafe/inline-asm.html"><strong aria-hidden="true">4.9.2.</strong> 内联汇编</a></li></ol></li><li class="chapter-item "><a href="../advance/macro.html"><strong aria-hidden="true">4.10.</strong> Macro 宏编程</a></li><li class="chapter-item "><a href="../advance/async/intro.html"><strong aria-hidden="true">4.11.</strong> async/await 异步编程</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance/async/getting-started.html"><strong aria-hidden="true">4.11.1.</strong> async 编程入门</a></li><li class="chapter-item "><a href="../advance/async/future-excuting.html"><strong aria-hidden="true">4.11.2.</strong> 底层探秘: Future 执行与任务调度</a></li><li class="chapter-item "><a href="../advance/async/pin-unpin.html"><strong aria-hidden="true">4.11.3.</strong> 定海神针 Pin 和 Unpin</a></li><li class="chapter-item "><a href="../advance/async/async-await.html"><strong aria-hidden="true">4.11.4.</strong> async/await 和 Stream 流处理</a></li><li class="chapter-item "><a href="../advance/async/multi-futures-simultaneous.html"><strong aria-hidden="true">4.11.5.</strong> 同时运行多个 Future</a></li><li class="chapter-item "><a href="../advance/async/pain-points-and-workarounds.html"><strong aria-hidden="true">4.11.6.</strong> 一些疑难问题的解决办法</a></li><li class="chapter-item "><a href="../advance/async/web-server.html"><strong aria-hidden="true">4.11.7.</strong> 实践应用：Async Web 服务器</a></li></ol></li></ol></li><li class="chapter-item "><a href="../advance-practice1/intro.html"><strong aria-hidden="true">5.</strong> 进阶实战1: 实现一个 web 服务器</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance-practice1/web-server.html"><strong aria-hidden="true">5.1.</strong> 单线程版本</a></li><li class="chapter-item "><a href="../advance-practice1/multi-threads.html"><strong aria-hidden="true">5.2.</strong> 多线程版本</a></li><li class="chapter-item "><a href="../advance-practice1/graceful-shutdown.html"><strong aria-hidden="true">5.3.</strong> 优雅关闭和资源清理</a></li></ol></li><li class="chapter-item "><a href="../advance-practice/intro.html"><strong aria-hidden="true">6.</strong> 进阶实战2: 实现一个简单 Redis</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../advance-practice/overview.html"><strong aria-hidden="true">6.1.</strong> tokio 概览</a></li><li class="chapter-item "><a href="../advance-practice/getting-startted.html"><strong aria-hidden="true">6.2.</strong> 使用初印象</a></li><li class="chapter-item "><a href="../advance-practice/spawning.html"><strong aria-hidden="true">6.3.</strong> 创建异步任务</a></li><li class="chapter-item "><a href="../advance-practice/shared-state.html"><strong aria-hidden="true">6.4.</strong> 共享状态</a></li><li class="chapter-item "><a href="../advance-practice/channels.html"><strong aria-hidden="true">6.5.</strong> 消息传递</a></li><li class="chapter-item "><a href="../advance-practice/io.html"><strong aria-hidden="true">6.6.</strong> I/O</a></li><li class="chapter-item "><a href="../advance-practice/frame.html"><strong aria-hidden="true">6.7.</strong> 解析数据帧</a></li><li class="chapter-item "><a href="../advance-practice/async.html"><strong aria-hidden="true">6.8.</strong> 深入 async</a></li><li class="chapter-item "><a href="../advance-practice/select.html"><strong aria-hidden="true">6.9.</strong> select</a></li><li class="chapter-item "><a href="../advance-practice/stream.html"><strong aria-hidden="true">6.10.</strong> 类似迭代器的 Stream</a></li><li class="chapter-item "><a href="../advance-practice/graceful-shutdown.html"><strong aria-hidden="true">6.11.</strong> 优雅的关闭</a></li><li class="chapter-item "><a href="../advance-practice/bridging-with-sync.html"><strong aria-hidden="true">6.12.</strong> 异步跟同步共存</a></li></ol></li><li class="chapter-item "><a href="../difficulties/intro.html"><strong aria-hidden="true">7.</strong> Rust 难点攻关</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../difficulties/slice.html"><strong aria-hidden="true">7.1.</strong> 切片和切片引用</a></li><li class="chapter-item "><a href="../difficulties/eq.html"><strong aria-hidden="true">7.2.</strong> Eq 和 PartialEq</a></li><li class="chapter-item "><a href="../difficulties/string.html"><strong aria-hidden="true">7.3.</strong> String、&str 和 str TODO</a></li><li class="chapter-item "><a href="../difficulties/lifetime.html"><strong aria-hidden="true">7.4.</strong> 作用域、生命周期和 NLL TODO</a></li><li class="chapter-item "><a href="../difficulties/move-copy.html"><strong aria-hidden="true">7.5.</strong> move、Copy 和 Clone TODO</a></li><li class="chapter-item "><a href="../advance/difficulties/pointer.html"><strong aria-hidden="true">7.6.</strong> 裸指针、引用和智能指针 TODO</a></li></ol></li><li class="chapter-item "><li class="part-title">常用工具链</li><li class="spacer"></li><li class="chapter-item "><a href="../test/intro.html"><strong aria-hidden="true">8.</strong> 自动化测试</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../test/write-tests.html"><strong aria-hidden="true">8.1.</strong> 编写测试及控制执行</a></li><li class="chapter-item "><a href="../test/unit-integration-test.html"><strong aria-hidden="true">8.2.</strong> 单元测试和集成测试</a></li><li class="chapter-item "><a href="../test/assertion.html"><strong aria-hidden="true">8.3.</strong> 断言 assertion</a></li><li class="chapter-item "><a href="../test/ci.html"><strong aria-hidden="true">8.4.</strong> 用 GitHub Actions 进行持续集成</a></li><li class="chapter-item "><a href="../test/benchmark.html"><strong aria-hidden="true">8.5.</strong> 基准测试 benchmark</a></li></ol></li><li class="chapter-item "><a href="../cargo/intro.html"><strong aria-hidden="true">9.</strong> Cargo 使用指南</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cargo/getting-started.html"><strong aria-hidden="true">9.1.</strong> 上手使用</a></li><li class="chapter-item "><a href="../cargo/guide/intro.html"><strong aria-hidden="true">9.2.</strong> 基础指南</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cargo/guide/why-exist.html"><strong aria-hidden="true">9.2.1.</strong> 为何会有 Cargo</a></li><li class="chapter-item "><a href="../cargo/guide/download-package.html"><strong aria-hidden="true">9.2.2.</strong> 下载并构建 Package</a></li><li class="chapter-item "><a href="../cargo/guide/dependencies.html"><strong aria-hidden="true">9.2.3.</strong> 添加依赖</a></li><li class="chapter-item "><a href="../cargo/guide/package-layout.html"><strong aria-hidden="true">9.2.4.</strong> Package 目录结构</a></li><li class="chapter-item "><a href="../cargo/guide/cargo-toml-lock.html"><strong aria-hidden="true">9.2.5.</strong> Cargo.toml vs Cargo.lock</a></li><li class="chapter-item "><a href="../cargo/guide/tests-ci.html"><strong aria-hidden="true">9.2.6.</strong> 测试和 CI</a></li><li class="chapter-item "><a href="../cargo/guide/cargo-cache.html"><strong aria-hidden="true">9.2.7.</strong> Cargo 缓存</a></li><li class="chapter-item "><a href="../cargo/guide/build-cache.html"><strong aria-hidden="true">9.2.8.</strong> Build 缓存</a></li></ol></li><li class="chapter-item "><a href="../cargo/reference/intro.html"><strong aria-hidden="true">9.3.</strong> 进阶指南</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cargo/reference/specify-deps.html"><strong aria-hidden="true">9.3.1.</strong> 指定依赖项</a></li><li class="chapter-item "><a href="../cargo/reference/deps-overriding.html"><strong aria-hidden="true">9.3.2.</strong> 依赖覆盖</a></li><li class="chapter-item "><a href="../cargo/reference/manifest.html"><strong aria-hidden="true">9.3.3.</strong> Cargo.toml 清单详解</a></li><li class="chapter-item "><a href="../cargo/reference/cargo-target.html"><strong aria-hidden="true">9.3.4.</strong> Cargo Target</a></li><li class="chapter-item "><a href="../cargo/reference/workspaces.html"><strong aria-hidden="true">9.3.5.</strong> 工作空间 Workspace</a></li><li class="chapter-item "><a href="../cargo/reference/features/intro.html"><strong aria-hidden="true">9.3.6.</strong> 条件编译 Features</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cargo/reference/features/examples.html"><strong aria-hidden="true">9.3.6.1.</strong> Features 示例</a></li></ol></li><li class="chapter-item "><a href="../cargo/reference/profiles.html"><strong aria-hidden="true">9.3.7.</strong> 发布配置 Profile</a></li><li class="chapter-item "><a href="../cargo/reference/configuration.html"><strong aria-hidden="true">9.3.8.</strong> 通过 config.toml 对 Cargo 进行配置</a></li><li class="chapter-item "><a href="../cargo/reference/publishing-on-crates.io.html"><strong aria-hidden="true">9.3.9.</strong> 发布到 crates.io</a></li><li class="chapter-item "><a href="../cargo/reference/build-script/intro.html"><strong aria-hidden="true">9.3.10.</strong> 构建脚本 build.rs</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../cargo/reference/build-script/examples.html"><strong aria-hidden="true">9.3.10.1.</strong> 构建脚本示例</a></li></ol></li></ol></li></ol></li><li class="chapter-item "><li class="part-title">开发实践</li><li class="spacer"></li><li class="chapter-item "><a href="../usecases/intro.html"><strong aria-hidden="true">10.</strong> 企业落地实践</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../usecases/aws-rust.html"><strong aria-hidden="true">10.1.</strong> AWS 为何这么喜欢 Rust?</a></li></ol></li><li class="chapter-item "><a href="../logs/intro.html"><strong aria-hidden="true">11.</strong> 日志和监控</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../logs/about-log.html"><strong aria-hidden="true">11.1.</strong> 日志详解</a></li><li class="chapter-item "><a href="../logs/log.html"><strong aria-hidden="true">11.2.</strong> 日志门面 log</a></li><li class="chapter-item "><a href="../logs/tracing.html"><strong aria-hidden="true">11.3.</strong> 使用 tracing 记录日志</a></li><li class="chapter-item "><a href="../logs/tracing-logger.html"><strong aria-hidden="true">11.4.</strong> 自定义 tracing 的输出格式</a></li><li class="chapter-item "><a href="../logs/observe/intro.html"><strong aria-hidden="true">11.5.</strong> 监控</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../logs/observe/about-observe.html"><strong aria-hidden="true">11.5.1.</strong> 可观测性</a></li><li class="chapter-item "><a href="../logs/observe/trace.html"><strong aria-hidden="true">11.5.2.</strong> 分布式追踪</a></li></ol></li></ol></li><li class="chapter-item "><a href="../practice/intro.html"><strong aria-hidden="true">12.</strong> Rust 最佳实践</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../practice/third-party-libs.html"><strong aria-hidden="true">12.1.</strong> 日常开发三方库精选</a></li><li class="chapter-item "><a href="../practice/naming.html"><strong aria-hidden="true">12.2.</strong> 命名规范</a></li><li class="chapter-item "><a href="../practice/interview.html"><strong aria-hidden="true">12.3.</strong> 面试经验</a></li><li class="chapter-item "><a href="../practice/best-pratice.html"><strong aria-hidden="true">12.4.</strong> 代码开发实践 todo</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/intro.html"><strong aria-hidden="true">13.</strong> 手把手带你实现链表</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/do-we-need-it.html"><strong aria-hidden="true">13.1.</strong> 我们到底需不需要链表</a></li><li class="chapter-item "><a href="../too-many-lists/bad-stack/intro.html"><strong aria-hidden="true">13.2.</strong> 不太优秀的单向链表：栈</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/bad-stack/layout.html"><strong aria-hidden="true">13.2.1.</strong> 数据布局</a></li><li class="chapter-item "><a href="../too-many-lists/bad-stack/basic-operations.html"><strong aria-hidden="true">13.2.2.</strong> 基本操作</a></li><li class="chapter-item "><a href="../too-many-lists/bad-stack/final-code.html"><strong aria-hidden="true">13.2.3.</strong> 最后实现</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/ok-stack/intro.html"><strong aria-hidden="true">13.3.</strong> 还可以的单向链表</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/ok-stack/type-optimizing.html"><strong aria-hidden="true">13.3.1.</strong> 优化类型定义</a></li><li class="chapter-item "><a href="../too-many-lists/ok-stack/peek.html"><strong aria-hidden="true">13.3.2.</strong> 定义 Peek 函数</a></li><li class="chapter-item "><a href="../too-many-lists/ok-stack/iter.html"><strong aria-hidden="true">13.3.3.</strong> IntoIter 和 Iter</a></li><li class="chapter-item "><a href="../too-many-lists/ok-stack/itermut.html"><strong aria-hidden="true">13.3.4.</strong> IterMut 以及完整代码</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/persistent-stack/intro.html"><strong aria-hidden="true">13.4.</strong> 持久化单向链表</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/persistent-stack/layout.html"><strong aria-hidden="true">13.4.1.</strong> 数据布局和基本操作</a></li><li class="chapter-item "><a href="../too-many-lists/persistent-stack/drop-arc.html"><strong aria-hidden="true">13.4.2.</strong> Drop、Arc 及完整代码</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/deque/intro.html"><strong aria-hidden="true">13.5.</strong> 不咋样的双端队列</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/deque/layout.html"><strong aria-hidden="true">13.5.1.</strong> 数据布局和基本操作</a></li><li class="chapter-item "><a href="../too-many-lists/deque/peek.html"><strong aria-hidden="true">13.5.2.</strong> Peek</a></li><li class="chapter-item "><a href="../too-many-lists/deque/symmetric.html"><strong aria-hidden="true">13.5.3.</strong> 基本操作的对称镜像</a></li><li class="chapter-item "><a href="../too-many-lists/deque/iterator.html"><strong aria-hidden="true">13.5.4.</strong> 迭代器</a></li><li class="chapter-item "><a href="../too-many-lists/deque/final-code.html"><strong aria-hidden="true">13.5.5.</strong> 最终代码</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/intro.html"><strong aria-hidden="true">13.6.</strong> 不错的 unsafe 队列</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/layout.html"><strong aria-hidden="true">13.6.1.</strong> 数据布局</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/basics.html"><strong aria-hidden="true">13.6.2.</strong> 基本操作</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/miri.html"><strong aria-hidden="true">13.6.3.</strong> Miri</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/stacked-borrow.html"><strong aria-hidden="true">13.6.4.</strong> 栈借用</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/testing-stacked-borrow.html"><strong aria-hidden="true">13.6.5.</strong> 测试栈借用</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/layout2.html"><strong aria-hidden="true">13.6.6.</strong> 数据布局 2</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/extra-junk.html"><strong aria-hidden="true">13.6.7.</strong> 额外的操作</a></li><li class="chapter-item "><a href="../too-many-lists/unsafe-queue/final-code.html"><strong aria-hidden="true">13.6.8.</strong> 最终代码</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/intro.html"><strong aria-hidden="true">13.7.</strong> 生产级的双向 unsafe 队列</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/layout.html"><strong aria-hidden="true">13.7.1.</strong> 数据布局</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/variance-and-phantomData.html"><strong aria-hidden="true">13.7.2.</strong> 型变与子类型</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/basics.html"><strong aria-hidden="true">13.7.3.</strong> 基础结构</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/drop-and-panic-safety.html"><strong aria-hidden="true">13.7.4.</strong> 恐慌与安全</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/boring-combinatorics.html"><strong aria-hidden="true">13.7.5.</strong> 无聊的组合</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/filling-in-random-bits.html"><strong aria-hidden="true">13.7.6.</strong> 其它特征</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/testing.html"><strong aria-hidden="true">13.7.7.</strong> 测试</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/send-sync-and-compile-tests.html"><strong aria-hidden="true">13.7.8.</strong> Send,Sync和编译测试</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/implementing-cursors.html"><strong aria-hidden="true">13.7.9.</strong> 实现游标</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/testing-cursors.html"><strong aria-hidden="true">13.7.10.</strong> 测试游标</a></li><li class="chapter-item "><a href="../too-many-lists/production-unsafe-deque/final-code.html"><strong aria-hidden="true">13.7.11.</strong> 最终代码</a></li></ol></li><li class="chapter-item "><a href="../too-many-lists/advanced-lists/intro.html"><strong aria-hidden="true">13.8.</strong> 使用高级技巧实现链表</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../too-many-lists/advanced-lists/double-singly.html"><strong aria-hidden="true">13.8.1.</strong> 双单向链表</a></li><li class="chapter-item "><a href="../too-many-lists/advanced-lists/stack-allocated.html"><strong aria-hidden="true">13.8.2.</strong> 栈上的链表</a></li></ol></li></ol></li><li class="chapter-item "><li class="part-title">攻克编译错误</li><li class="spacer"></li><li class="chapter-item "><a href="../compiler/intro.html"><strong aria-hidden="true">14.</strong> 征服编译错误</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../compiler/fight-with-compiler/intro.html"><strong aria-hidden="true">14.1.</strong> 对抗编译检查</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../compiler/fight-with-compiler/lifetime/intro.html"><strong aria-hidden="true">14.1.1.</strong> 生命周期</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../compiler/fight-with-compiler/lifetime/too-long1.html"><strong aria-hidden="true">14.1.1.1.</strong> 生命周期过大-01</a></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/lifetime/too-long2.html"><strong aria-hidden="true">14.1.1.2.</strong> 生命周期过大-02</a></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/lifetime/loop.html"><strong aria-hidden="true">14.1.1.3.</strong> 循环中的生命周期</a></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/lifetime/closure-with-static.html"><strong aria-hidden="true">14.1.1.4.</strong> 闭包碰到特征对象-01</a></li></ol></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/borrowing/intro.html"><strong aria-hidden="true">14.1.2.</strong> 重复借用</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../compiler/fight-with-compiler/borrowing/ref-exist-in-out-fn.html"><strong aria-hidden="true">14.1.2.1.</strong> 同时在函数内外使用引用</a></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/borrowing/borrow-distinct-fields-of-struct.html"><strong aria-hidden="true">14.1.2.2.</strong> 智能指针引起的重复借用错误</a></li></ol></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/unconstrained.html"><strong aria-hidden="true">14.1.3.</strong> 类型未限制(todo)</a></li><li class="chapter-item "><a href="../compiler/fight-with-compiler/phantom-data.html"><strong aria-hidden="true">14.1.4.</strong> 幽灵数据(todo)</a></li></ol></li><li class="chapter-item "><a href="../compiler/pitfalls/index.html"><strong aria-hidden="true">14.2.</strong> Rust 常见陷阱</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../compiler/pitfalls/use-vec-in-for.html"><strong aria-hidden="true">14.2.1.</strong> for 循环中使用外部数组</a></li><li class="chapter-item "><a href="../compiler/pitfalls/stack-overflow.html"><strong aria-hidden="true">14.2.2.</strong> 线程类型导致的栈溢出</a></li><li class="chapter-item "><a href="../compiler/pitfalls/arithmetic-overflow.html"><strong aria-hidden="true">14.2.3.</strong> 算术溢出导致的 panic</a></li><li class="chapter-item "><a href="../compiler/pitfalls/closure-with-lifetime.html"><strong aria-hidden="true">14.2.4.</strong> 闭包中奇怪的生命周期</a></li><li class="chapter-item "><a href="../compiler/pitfalls/the-disabled-mutability.html"><strong aria-hidden="true">14.2.5.</strong> 可变变量不可变？</a></li><li class="chapter-item "><a href="../compiler/pitfalls/multiple-mutable-references.html"><strong aria-hidden="true">14.2.6.</strong> 可变借用失败引发的深入思考</a></li><li class="chapter-item "><a href="../compiler/pitfalls/lazy-iterators.html"><strong aria-hidden="true">14.2.7.</strong> 不太勤快的迭代器</a></li><li class="chapter-item "><a href="../compiler/pitfalls/weird-ranges.html"><strong aria-hidden="true">14.2.8.</strong> 奇怪的序列 x..y</a></li><li class="chapter-item "><a href="../compiler/pitfalls/iterator-everywhere.html"><strong aria-hidden="true">14.2.9.</strong> 无处不在的迭代器</a></li><li class="chapter-item "><a href="../compiler/pitfalls/main-with-channel-blocked.html"><strong aria-hidden="true">14.2.10.</strong> 线程间传递消息导致主线程无法结束</a></li><li class="chapter-item "><a href="../compiler/pitfalls/utf8-performance.html"><strong aria-hidden="true">14.2.11.</strong> 警惕 UTF-8 引发的性能隐患</a></li></ol></li></ol></li><li class="chapter-item "><li class="part-title">性能优化</li><li class="spacer"></li><li class="chapter-item "><a href="../profiling/intro.html"><strong aria-hidden="true">15.</strong> Rust 性能优化 todo</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../profiling/memory/intro.html"><strong aria-hidden="true">15.1.</strong> 深入内存 todo</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../profiling/memory/pointer-ref.html"><strong aria-hidden="true">15.1.1.</strong> 指针和引用 todo</a></li><li class="chapter-item "><a href="../profiling/memory/uninit.html"><strong aria-hidden="true">15.1.2.</strong> 未初始化内存 todo</a></li><li class="chapter-item "><a href="../profiling/memory/allocation.html"><strong aria-hidden="true">15.1.3.</strong> 内存分配 todo</a></li><li class="chapter-item "><a href="../profiling/memory/layout.html"><strong aria-hidden="true">15.1.4.</strong> 内存布局 todo</a></li><li class="chapter-item "><a href="../profiling/memory/virtual.html"><strong aria-hidden="true">15.1.5.</strong> 虚拟内存 todo</a></li></ol></li><li class="chapter-item "><a href="../profiling/performance/intro.html"><strong aria-hidden="true">15.2.</strong> 性能调优 doing</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../profiling/performance/string.html"><strong aria-hidden="true">15.2.1.</strong> 字符串操作性能</a></li><li class="chapter-item "><a href="../profiling/performance/deep-into-move.html"><strong aria-hidden="true">15.2.2.</strong> 深入理解 move</a></li><li class="chapter-item "><a href="../profiling/performance/early-optimise.html"><strong aria-hidden="true">15.2.3.</strong> 糟糕的提前优化 todo</a></li><li class="chapter-item "><a href="../profiling/performance/clone-copy.html"><strong aria-hidden="true">15.2.4.</strong> Clone 和 Copy todo</a></li><li class="chapter-item "><a href="../profiling/performance/runtime-check.html"><strong aria-hidden="true">15.2.5.</strong> 减少 Runtime check(todo)</a></li><li class="chapter-item "><a href="../profiling/performance/cpu-cache.html"><strong aria-hidden="true">15.2.6.</strong> CPU 缓存性能优化 todo</a></li><li class="chapter-item "><a href="../profiling/performance/calculate.html"><strong aria-hidden="true">15.2.7.</strong> 计算性能优化 todo</a></li><li class="chapter-item "><a href="../profiling/performance/heap-stack.html"><strong aria-hidden="true">15.2.8.</strong> 堆和栈 todo</a></li><li class="chapter-item "><a href="../profiling/performance/allocator.html"><strong aria-hidden="true">15.2.9.</strong> 内存 allocator todo</a></li><li class="chapter-item "><a href="../profiling/performance/tools.html"><strong aria-hidden="true">15.2.10.</strong> 常用性能测试工具 todo</a></li><li class="chapter-item "><a href="../profiling/performance/enum.html"><strong aria-hidden="true">15.2.11.</strong> Enum 内存优化 todo</a></li></ol></li><li class="chapter-item "><a href="../profiling/compiler/intro.html"><strong aria-hidden="true">15.3.</strong> 编译优化 todo</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../profiling/compiler/llvm.html"><strong aria-hidden="true">15.3.1.</strong> LLVM todo</a></li><li class="chapter-item "><a href="../profiling/compiler/attributes.html"><strong aria-hidden="true">15.3.2.</strong> 常见属性标记 todo</a></li><li class="chapter-item "><a href="../profiling/compiler/speed-up.html"><strong aria-hidden="true">15.3.3.</strong> 提升编译速度 todo</a></li><li class="chapter-item "><a href="../profiling/compiler/optimization/intro.html"><strong aria-hidden="true">15.3.4.</strong> 编译器优化 todo</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../profiling/compiler/optimization/option.html"><strong aria-hidden="true">15.3.4.1.</strong> Option 枚举 todo</a></li></ol></li></ol></li></ol></li><li class="chapter-item "><li class="part-title">附录</li><li class="spacer"></li><li class="chapter-item "><div><strong aria-hidden="true">16.</strong> Appendix</div><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../appendix/keywords.html"><strong aria-hidden="true">16.1.</strong> 关键字</a></li><li class="chapter-item "><a href="../appendix/operators.html"><strong aria-hidden="true">16.2.</strong> 运算符与符号</a></li><li class="chapter-item "><a href="../appendix/expressions.html"><strong aria-hidden="true">16.3.</strong> 表达式</a></li><li class="chapter-item "><a href="../appendix/derive.html"><strong aria-hidden="true">16.4.</strong> 派生特征 trait</a></li><li class="chapter-item "><a href="../appendix/prelude.html"><strong aria-hidden="true">16.5.</strong> prelude 模块 todo</a></li><li class="chapter-item "><a href="../appendix/rust-version.html"><strong aria-hidden="true">16.6.</strong> Rust 版本说明</a></li><li class="chapter-item "><a href="../appendix/rust-versions/intro.html"><strong aria-hidden="true">16.7.</strong> Rust 历次版本更新解读</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../appendix/rust-versions/1.58.html"><strong aria-hidden="true">16.7.1.</strong> 1.58</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.59.html"><strong aria-hidden="true">16.7.2.</strong> 1.59</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.60.html"><strong aria-hidden="true">16.7.3.</strong> 1.60</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.61.html"><strong aria-hidden="true">16.7.4.</strong> 1.61</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.62.html"><strong aria-hidden="true">16.7.5.</strong> 1.62</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.63.html"><strong aria-hidden="true">16.7.6.</strong> 1.63</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.64.html"><strong aria-hidden="true">16.7.7.</strong> 1.64</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.65.html"><strong aria-hidden="true">16.7.8.</strong> 1.65</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.66.html"><strong aria-hidden="true">16.7.9.</strong> 1.66</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.67.html"><strong aria-hidden="true">16.7.10.</strong> 1.67</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.68.html"><strong aria-hidden="true">16.7.11.</strong> 1.68</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.69.html"><strong aria-hidden="true">16.7.12.</strong> 1.69</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.70.html"><strong aria-hidden="true">16.7.13.</strong> 1.70</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.71.html"><strong aria-hidden="true">16.7.14.</strong> 1.71</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.72.html"><strong aria-hidden="true">16.7.15.</strong> 1.72</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.73.html"><strong aria-hidden="true">16.7.16.</strong> 1.73</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.74.html"><strong aria-hidden="true">16.7.17.</strong> 1.74</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.75.html"><strong aria-hidden="true">16.7.18.</strong> 1.75</a></li><li class="chapter-item "><a href="../appendix/rust-versions/1.76.html"><strong aria-hidden="true">16.7.19.</strong> 1.76</a></li></ol></li></ol></li></ol>
</div>
<div id="sidebar-resize-handle" class="sidebar-resize-handle">
<div class="sidebar-resize-indicator"></div>
</div>
</nav>
<!-- Track and set sidebar scroll position -->
<script>
var sidebarScrollbox = document.querySelector('#sidebar .sidebar-scrollbox');
sidebarScrollbox.addEventListener('click', function(e) {
if (e.target.tagName === 'A') {
sessionStorage.setItem('sidebar-scroll', sidebarScrollbox.scrollTop);
}
}, { passive: true });
var sidebarScrollTop = sessionStorage.getItem('sidebar-scroll');
sessionStorage.removeItem('sidebar-scroll');
if (sidebarScrollTop) {
// preserve sidebar scroll position when navigating via links within sidebar
sidebarScrollbox.scrollTop = sidebarScrollTop;
} else {
// scroll sidebar to current active section when navigating via "next/previous chapter" buttons
var activeSection = document.querySelector('#sidebar .active');
if (activeSection) {
activeSection.scrollIntoView({ block: 'center' });
}
}
</script>
<div id="page-wrapper" class="page-wrapper">
<div class="page">
<div id="menu-bar-hover-placeholder"></div>
<div id="menu-bar" class="menu-bar sticky">
<div class="left-buttons">
<label id="sidebar-toggle" class="icon-button" for="sidebar-toggle-anchor" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
<i class="fa fa-bars"></i>
</label>
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
<i class="fa fa-paint-brush"></i>
</button>
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
<li role="none"><button role="menuitem" class="theme" id="light">Light</button></li>
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
</ul>
<button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
<i class="fa fa-search"></i>
</button>
</div>
<h1 class="menu-title">Rust语言圣经(Rust Course)</h1>
<div class="right-buttons">
<a href="../print.html" title="Print this book" aria-label="Print this book">
<i id="print-button" class="fa fa-print"></i>
</a>
<a href="https://github.com/sunface/rust-course" title="Git repository" aria-label="Git repository">
<i id="git-repository-button" class="fa fa-github"></i>
</a>
<a href="https://github.com/sunface/rust-course/edit/main/src/advance/errors.md" title="Suggest an edit" aria-label="Suggest an edit">
<i id="git-edit-button" class="fa fa-edit"></i>
</a>
</div>
</div>
<div id="search-wrapper" class="hidden">
<form id="searchbar-outer" class="searchbar-outer">
<input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
</form>
<div id="searchresults-outer" class="searchresults-outer hidden">
<div id="searchresults-header" class="searchresults-header"></div>
<ul id="searchresults">
</ul>
</div>
</div>
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
<script>
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
});
</script>
<div id="content" class="content">
<!-- Page table of contents -->
<div class="sidetoc"><nav class="pagetoc"></nav></div>
<main>
<h1 id="错误处理"><a class="header" href="#错误处理">错误处理</a></h1>
<p>在之前的<a href="https://course.rs/basic/result-error/intro.html">返回值和错误处理</a>章节中，我们学习了几个重要的概念，例如 <code>Result</code> 用于返回结果处理，<code>?</code> 用于错误的传播，若大家对此还较为模糊，强烈建议回头温习下。</p>
<p>在本章节中一起来看看如何对 <code>Result</code> ( <code>Option</code> ) 做进一步的处理，以及如何定义自己的错误类型。</p>
<h2 id="组合器"><a class="header" href="#组合器">组合器</a></h2>
<p>在设计模式中，有一个组合器模式，相信有 Java 背景的同学对此并不陌生。</p>
<blockquote>
<p>将对象组合成树形结构以表示“部分整体”的层次结构。组合模式使得用户对单个对象和组合对象的使用具有一致性。–GoF &lt;&lt;设计模式&gt;&gt;</p>
</blockquote>
<p>与组合器模式有所不同，在 Rust 中，组合器更多的是用于对返回结果的类型进行变换：例如使用 <code>ok_or</code> 将一个 <code>Option</code> 类型转换成 <code>Result</code> 类型。</p>
<p>下面我们来看看一些常见的组合器。</p>
<h4 id="or-和-and"><a class="header" href="#or-和-and">or() 和 and()</a></h4>
<p>跟布尔关系的与/或很像，这两个方法会对两个表达式做逻辑组合，最终返回 <code>Option</code> / <code>Result</code>。</p>
<ul>
<li><code>or()</code>，表达式按照顺序求值，若任何一个表达式的结果是 <code>Some</code> 或 <code>Ok</code>，则该值会立刻返回</li>
<li><code>and()</code>，若两个表达式的结果都是 <code>Some</code> 或 <code>Ok</code>，则<strong>第二个表达式中的值被返回</strong>。若任何一个的结果是 <code>None</code> 或 <code>Err</code> ，则立刻返回。</li>
</ul>
<p>实际上，只要将布尔表达式的 <code>true</code> / <code>false</code>，替换成 <code>Some</code> / <code>None</code> 或 <code>Ok</code> / <code>Err</code> 就很好理解了。</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
let s1 = Some(&quot;some1&quot;);
let s2 = Some(&quot;some2&quot;);
let n: Option&lt;&amp;str&gt; = None;
let o1: Result&lt;&amp;str, &amp;str&gt; = Ok(&quot;ok1&quot;);
let o2: Result&lt;&amp;str, &amp;str&gt; = Ok(&quot;ok2&quot;);
let e1: Result&lt;&amp;str, &amp;str&gt; = Err(&quot;error1&quot;);
let e2: Result&lt;&amp;str, &amp;str&gt; = Err(&quot;error2&quot;);
assert_eq!(s1.or(s2), s1); // Some1 or Some2 = Some1
assert_eq!(s1.or(n), s1); // Some or None = Some
assert_eq!(n.or(s1), s1); // None or Some = Some
assert_eq!(n.or(n), n); // None1 or None2 = None2
assert_eq!(o1.or(o2), o1); // Ok1 or Ok2 = Ok1
assert_eq!(o1.or(e1), o1); // Ok or Err = Ok
assert_eq!(e1.or(o1), o1); // Err or Ok = Ok
assert_eq!(e1.or(e2), e2); // Err1 or Err2 = Err2
assert_eq!(s1.and(s2), s2); // Some1 and Some2 = Some2
assert_eq!(s1.and(n), n); // Some and None = None
assert_eq!(n.and(s1), n); // None and Some = None
assert_eq!(n.and(n), n); // None1 and None2 = None1
assert_eq!(o1.and(o2), o2); // Ok1 and Ok2 = Ok2
assert_eq!(o1.and(e1), e1); // Ok and Err = Err
assert_eq!(e1.and(o1), e1); // Err and Ok = Err
assert_eq!(e1.and(e2), e1); // Err1 and Err2 = Err1
}</code></pre></pre>
<p>除了 <code>or</code> 和 <code>and</code> 之外，Rust 还为我们提供了 <code>xor</code> ，但是它只能应用在 <code>Option</code> 上，其实想想也是这个理，如果能应用在 <code>Result</code> 上，那你又该如何对一个值和错误进行异或操作？</p>
<h4 id="or_else-和-and_then"><a class="header" href="#or_else-和-and_then">or_else() 和 and_then()</a></h4>
<p>它们跟 <code>or()</code> 和 <code>and()</code> 类似，唯一的区别在于，它们的第二个表达式是一个闭包。</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
// or_else with Option
let s1 = Some(&quot;some1&quot;);
let s2 = Some(&quot;some2&quot;);
let fn_some = || Some(&quot;some2&quot;); // 类似于: let fn_some = || -&gt; Option&lt;&amp;str&gt; { Some(&quot;some2&quot;) };
let n: Option&lt;&amp;str&gt; = None;
let fn_none = || None;
assert_eq!(s1.or_else(fn_some), s1); // Some1 or_else Some2 = Some1
assert_eq!(s1.or_else(fn_none), s1); // Some or_else None = Some
assert_eq!(n.or_else(fn_some), s2); // None or_else Some = Some
assert_eq!(n.or_else(fn_none), None); // None1 or_else None2 = None2
// or_else with Result
let o1: Result&lt;&amp;str, &amp;str&gt; = Ok(&quot;ok1&quot;);
let o2: Result&lt;&amp;str, &amp;str&gt; = Ok(&quot;ok2&quot;);
let fn_ok = |_| Ok(&quot;ok2&quot;); // 类似于: let fn_ok = |_| -&gt; Result&lt;&amp;str, &amp;str&gt; { Ok(&quot;ok2&quot;) };
let e1: Result&lt;&amp;str, &amp;str&gt; = Err(&quot;error1&quot;);
let e2: Result&lt;&amp;str, &amp;str&gt; = Err(&quot;error2&quot;);
let fn_err = |_| Err(&quot;error2&quot;);
assert_eq!(o1.or_else(fn_ok), o1); // Ok1 or_else Ok2 = Ok1
assert_eq!(o1.or_else(fn_err), o1); // Ok or_else Err = Ok
assert_eq!(e1.or_else(fn_ok), o2); // Err or_else Ok = Ok
assert_eq!(e1.or_else(fn_err), e2); // Err1 or_else Err2 = Err2
}</code></pre></pre>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
// and_then with Option
let s1 = Some(&quot;some1&quot;);
let s2 = Some(&quot;some2&quot;);
let fn_some = |_| Some(&quot;some2&quot;); // 类似于: let fn_some = |_| -&gt; Option&lt;&amp;str&gt; { Some(&quot;some2&quot;) };
let n: Option&lt;&amp;str&gt; = None;
let fn_none = |_| None;
assert_eq!(s1.and_then(fn_some), s2); // Some1 and_then Some2 = Some2
assert_eq!(s1.and_then(fn_none), n); // Some and_then None = None
assert_eq!(n.and_then(fn_some), n); // None and_then Some = None
assert_eq!(n.and_then(fn_none), n); // None1 and_then None2 = None1
// and_then with Result
let o1: Result&lt;&amp;str, &amp;str&gt; = Ok(&quot;ok1&quot;);
let o2: Result&lt;&amp;str, &amp;str&gt; = Ok(&quot;ok2&quot;);
let fn_ok = |_| Ok(&quot;ok2&quot;); // 类似于: let fn_ok = |_| -&gt; Result&lt;&amp;str, &amp;str&gt; { Ok(&quot;ok2&quot;) };
let e1: Result&lt;&amp;str, &amp;str&gt; = Err(&quot;error1&quot;);
let e2: Result&lt;&amp;str, &amp;str&gt; = Err(&quot;error2&quot;);
let fn_err = |_| Err(&quot;error2&quot;);
assert_eq!(o1.and_then(fn_ok), o2); // Ok1 and_then Ok2 = Ok2
assert_eq!(o1.and_then(fn_err), e2); // Ok and_then Err = Err
assert_eq!(e1.and_then(fn_ok), e1); // Err and_then Ok = Err
assert_eq!(e1.and_then(fn_err), e1); // Err1 and_then Err2 = Err1
}</code></pre></pre>
<h4 id="filter"><a class="header" href="#filter">filter</a></h4>
<p><code>filter</code> 用于对 <code>Option</code> 进行过滤：</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
let s1 = Some(3);
let s2 = Some(6);
let n = None;
let fn_is_even = |x: &amp;i8| x % 2 == 0;
assert_eq!(s1.filter(fn_is_even), n); // Some(3) -&gt; 3 is not even -&gt; None
assert_eq!(s2.filter(fn_is_even), s2); // Some(6) -&gt; 6 is even -&gt; Some(6)
assert_eq!(n.filter(fn_is_even), n); // None -&gt; no value -&gt; None
}</code></pre></pre>
<h4 id="map-和-map_err"><a class="header" href="#map-和-map_err">map() 和 map_err()</a></h4>
<p><code>map</code> 可以将 <code>Some</code> 或 <code>Ok</code> 中的值映射为另一个：</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
let s1 = Some(&quot;abcde&quot;);
let s2 = Some(5);
let n1: Option&lt;&amp;str&gt; = None;
let n2: Option&lt;usize&gt; = None;
let o1: Result&lt;&amp;str, &amp;str&gt; = Ok(&quot;abcde&quot;);
let o2: Result&lt;usize, &amp;str&gt; = Ok(5);
let e1: Result&lt;&amp;str, &amp;str&gt; = Err(&quot;abcde&quot;);
let e2: Result&lt;usize, &amp;str&gt; = Err(&quot;abcde&quot;);
let fn_character_count = |s: &amp;str| s.chars().count();
assert_eq!(s1.map(fn_character_count), s2); // Some1 map = Some2
assert_eq!(n1.map(fn_character_count), n2); // None1 map = None2
assert_eq!(o1.map(fn_character_count), o2); // Ok1 map = Ok2
assert_eq!(e1.map(fn_character_count), e2); // Err1 map = Err2
}</code></pre></pre>
<p>但是如果你想要将 <code>Err</code> 中的值进行改变， <code>map</code> 就无能为力了，此时我们需要用 <code>map_err</code>：</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
let o1: Result&lt;&amp;str, &amp;str&gt; = Ok(&quot;abcde&quot;);
let o2: Result&lt;&amp;str, isize&gt; = Ok(&quot;abcde&quot;);
let e1: Result&lt;&amp;str, &amp;str&gt; = Err(&quot;404&quot;);
let e2: Result&lt;&amp;str, isize&gt; = Err(404);
let fn_character_count = |s: &amp;str| -&gt; isize { s.parse().unwrap() }; // 该函数返回一个 isize
assert_eq!(o1.map_err(fn_character_count), o2); // Ok1 map = Ok2
assert_eq!(e1.map_err(fn_character_count), e2); // Err1 map = Err2
}</code></pre></pre>
<p>通过对 <code>o1</code> 的操作可以看出，与 <code>map</code> 面对 <code>Err</code> 时的短小类似， <code>map_err</code> 面对 <code>Ok</code> 时也是相当无力的。</p>
<h4 id="map_or-和-map_or_else"><a class="header" href="#map_or-和-map_or_else">map_or() 和 map_or_else()</a></h4>
<p><code>map_or</code> 在 <code>map</code> 的基础上提供了一个默认值:</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
const V_DEFAULT: u32 = 1;
let s: Result&lt;u32, ()&gt; = Ok(10);
let n: Option&lt;u32&gt; = None;
let fn_closure = |v: u32| v + 2;
assert_eq!(s.map_or(V_DEFAULT, fn_closure), 12);
assert_eq!(n.map_or(V_DEFAULT, fn_closure), V_DEFAULT);
}</code></pre></pre>
<p>如上所示，当处理 <code>None</code> 的时候，<code>V_DEFAULT</code> 作为默认值被直接返回。</p>
<p><code>map_or_else</code> 与 <code>map_or</code> 类似，但是它是通过一个闭包来提供默认值:</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
let s = Some(10);
let n: Option&lt;i8&gt; = None;
let fn_closure = |v: i8| v + 2;
let fn_default = || 1;
assert_eq!(s.map_or_else(fn_default, fn_closure), 12);
assert_eq!(n.map_or_else(fn_default, fn_closure), 1);
let o = Ok(10);
let e = Err(5);
let fn_default_for_result = |v: i8| v + 1; // 闭包可以对 Err 中的值进行处理，并返回一个新值
assert_eq!(o.map_or_else(fn_default_for_result, fn_closure), 12);
assert_eq!(e.map_or_else(fn_default_for_result, fn_closure), 6);
}</code></pre></pre>
<h4 id="ok_or-and-ok_or_else"><a class="header" href="#ok_or-and-ok_or_else">ok_or() and ok_or_else()</a></h4>
<p>这两兄弟可以将 <code>Option</code> 类型转换为 <code>Result</code> 类型。其中 <code>ok_or</code> 接收一个默认的 <code>Err</code> 参数:</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
const ERR_DEFAULT: &amp;str = &quot;error message&quot;;
let s = Some(&quot;abcde&quot;);
let n: Option&lt;&amp;str&gt; = None;
let o: Result&lt;&amp;str, &amp;str&gt; = Ok(&quot;abcde&quot;);
let e: Result&lt;&amp;str, &amp;str&gt; = Err(ERR_DEFAULT);
assert_eq!(s.ok_or(ERR_DEFAULT), o); // Some(T) -&gt; Ok(T)
assert_eq!(n.ok_or(ERR_DEFAULT), e); // None -&gt; Err(default)
}</code></pre></pre>
<p>而 <code>ok_or_else</code> 接收一个闭包作为 <code>Err</code> 参数:</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
let s = Some(&quot;abcde&quot;);
let n: Option&lt;&amp;str&gt; = None;
let fn_err_message = || &quot;error message&quot;;
let o: Result&lt;&amp;str, &amp;str&gt; = Ok(&quot;abcde&quot;);
let e: Result&lt;&amp;str, &amp;str&gt; = Err(&quot;error message&quot;);
assert_eq!(s.ok_or_else(fn_err_message), o); // Some(T) -&gt; Ok(T)
assert_eq!(n.ok_or_else(fn_err_message), e); // None -&gt; Err(default)
}</code></pre></pre>
<p>以上列出的只是常用的一部分，强烈建议大家看看标准库中有哪些可用的 API，在实际项目中，这些 API 将会非常有用: <a href="https://doc.rust-lang.org/stable/std/option/enum.Option.html">Option</a> 和 <a href="https://doc.rust-lang.org/stable/std/result/enum.Result.html">Result</a>。</p>
<h2 id="自定义错误类型"><a class="header" href="#自定义错误类型">自定义错误类型</a></h2>
<p>虽然标准库定义了大量的错误类型，但是一个严谨的项目，光使用这些错误类型往往是不够的，例如我们可能会为暴露给用户的错误定义相应的类型。</p>
<p>为了帮助我们更好的定义错误，Rust 在标准库中提供了一些可复用的特征，例如 <code>std::error::Error</code> 特征：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>use std::fmt::{Debug, Display};
pub trait Error: Debug + Display {
fn source(&amp;self) -&gt; Option&lt;&amp;(Error + 'static)&gt; { ... }
}
<span class="boring">}</span></code></pre></pre>
<p>当自定义类型实现该特征后，该类型就可以作为 <code>Err</code> 来使用，下面一起来看看。</p>
<blockquote>
<p>实际上，自定义错误类型只需要实现 <code>Debug</code> 和 <code>Display</code> 特征即可，<code>source</code> 方法是可选的，而 <code>Debug</code> 特征往往也无需手动实现，可以直接通过 <code>derive</code> 来派生</p>
</blockquote>
<h4 id="最简单的错误"><a class="header" href="#最简单的错误">最简单的错误</a></h4>
<pre><pre class="playground"><code class="language-rust edition2021">use std::fmt;
// AppError 是自定义错误类型，它可以是当前包中定义的任何类型，在这里为了简化，我们使用了单元结构体作为例子。
// 为 AppError 自动派生 Debug 特征
#[derive(Debug)]
struct AppError;
// 为 AppError 实现 std::fmt::Display 特征
impl fmt::Display for AppError {
fn fmt(&amp;self, f: &amp;mut fmt::Formatter) -&gt; fmt::Result {
write!(f, &quot;An Error Occurred, Please Try Again!&quot;) // user-facing output
}
}
// 一个示例函数用于产生 AppError 错误
fn produce_error() -&gt; Result&lt;(), AppError&gt; {
Err(AppError)
}
fn main(){
match produce_error() {
Err(e) =&gt; eprintln!(&quot;{}&quot;, e),
_ =&gt; println!(&quot;No error&quot;),
}
eprintln!(&quot;{:?}&quot;, produce_error()); // Err({ file: src/main.rs, line: 17 })
}</code></pre></pre>
<p>上面的例子很简单，我们定义了一个错误类型，当为它派生了 <code>Debug</code> 特征，同时手动实现了 <code>Display</code> 特征后，该错误类型就可以作为 <code>Err</code>来使用了。</p>
<p>事实上，实现 <code>Debug</code> 和 <code>Display</code> 特征并不是作为 <code>Err</code> 使用的必要条件，大家可以把这两个特征实现和相应使用去除，然后看看代码会否报错。既然如此，我们为何要为自定义类型实现这两个特征呢？原因有二:</p>
<ul>
<li>错误得打印输出后，才能有实际用处，而打印输出就需要实现这两个特征</li>
<li>可以将自定义错误转换成 <code>Box&lt;dyn std::error:Error&gt;</code> 特征对象，在后面的<strong>归一化不同错误类型</strong>部分，我们会详细介绍</li>
</ul>
<h4 id="更详尽的错误"><a class="header" href="#更详尽的错误">更详尽的错误</a></h4>
<p>上一个例子中定义的错误非常简单，我们无法从错误中得到更多的信息，现在再来定义一个具有错误码和信息的错误:</p>
<pre><pre class="playground"><code class="language-rust edition2021">use std::fmt;
struct AppError {
code: usize,
message: String,
}
// 根据错误码显示不同的错误信息
impl fmt::Display for AppError {
fn fmt(&amp;self, f: &amp;mut fmt::Formatter) -&gt; fmt::Result {
let err_msg = match self.code {
404 =&gt; &quot;Sorry, Can not find the Page!&quot;,
_ =&gt; &quot;Sorry, something is wrong! Please Try Again!&quot;,
};
write!(f, &quot;{}&quot;, err_msg)
}
}
impl fmt::Debug for AppError {
fn fmt(&amp;self, f: &amp;mut fmt::Formatter) -&gt; fmt::Result {
write!(
f,
&quot;AppError {{ code: {}, message: {} }}&quot;,
self.code, self.message
)
}
}
fn produce_error() -&gt; Result&lt;(), AppError&gt; {
Err(AppError {
code: 404,
message: String::from(&quot;Page not found&quot;),
})
}
fn main() {
match produce_error() {
Err(e) =&gt; eprintln!(&quot;{}&quot;, e), // 抱歉，未找到指定的页面!
_ =&gt; println!(&quot;No error&quot;),
}
eprintln!(&quot;{:?}&quot;, produce_error()); // Err(AppError { code: 404, message: Page not found })
eprintln!(&quot;{:#?}&quot;, produce_error());
// Err(
// AppError { code: 404, message: Page not found }
// )
}</code></pre></pre>
<p>在本例中，我们除了增加了错误码和消息外，还手动实现了 <code>Debug</code> 特征，原因在于，我们希望能自定义 <code>Debug</code> 的输出内容，而不是使用派生后系统提供的默认输出形式。</p>
<h4 id="错误转换-from-特征"><a class="header" href="#错误转换-from-特征">错误转换 <code>From</code> 特征</a></h4>
<p>标准库、三方库、本地库，各有各的精彩，各也有各的错误。那么问题就来了，我们该如何将其它的错误类型转换成自定义的错误类型？总不能神鬼牛魔，同台共舞吧。。</p>
<p>好在 Rust 为我们提供了 <code>std::convert::From</code> 特征:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub trait From&lt;T&gt;: Sized {
fn from(_: T) -&gt; Self;
}
<span class="boring">}</span></code></pre></pre>
<blockquote>
<p>事实上，该特征在之前的 <a href="https://course.rs/basic/result-error/result.html#%E4%BC%A0%E6%92%AD%E7%95%8C%E7%9A%84%E5%A4%A7%E6%98%8E%E6%98%9F-"><code>?</code> 操作符</a>章节中就有所介绍。</p>
<p>大家都使用过 <code>String::from</code> 函数吧？它可以通过 <code>&amp;str</code> 来创建一个 <code>String</code>，其实该函数就是 <code>From</code> 特征提供的</p>
</blockquote>
<p>下面一起来看看如何为自定义类型实现 <code>From</code> 特征:</p>
<pre><pre class="playground"><code class="language-rust edition2021">use std::fs::File;
use std::io;
#[derive(Debug)]
struct AppError {
kind: String, // 错误类型
message: String, // 错误信息
}
// 为 AppError 实现 std::convert::From 特征，由于 From 包含在 std::prelude 中，因此可以直接简化引入。
// 实现 From&lt;io::Error&gt; 意味着我们可以将 io::Error 错误转换成自定义的 AppError 错误
impl From&lt;io::Error&gt; for AppError {
fn from(error: io::Error) -&gt; Self {
AppError {
kind: String::from(&quot;io&quot;),
message: error.to_string(),
}
}
}
fn main() -&gt; Result&lt;(), AppError&gt; {
let _file = File::open(&quot;nonexistent_file.txt&quot;)?;
Ok(())
}
// --------------- 上述代码运行后输出 ---------------
Error: AppError { kind: &quot;io&quot;, message: &quot;No such file or directory (os error 2)&quot; }</code></pre></pre>
<p>上面的代码中除了实现 <code>From</code> 外，还有一点特别重要，那就是 <code>?</code> 可以将错误进行隐式的强制转换：<code>File::open</code> 返回的是 <code>std::io::Error</code>， 我们并没有进行任何显式的转换，它就能自动变成 <code>AppError</code> ，这就是 <code>?</code> 的强大之处！</p>
<p>上面的例子只有一个标准库错误，再来看看多个不同的错误转换成 <code>AppError</code> 的实现：</p>
<pre><pre class="playground"><code class="language-rust edition2021">use std::fs::File;
use std::io::{self, Read};
use std::num;
#[derive(Debug)]
struct AppError {
kind: String,
message: String,
}
impl From&lt;io::Error&gt; for AppError {
fn from(error: io::Error) -&gt; Self {
AppError {
kind: String::from(&quot;io&quot;),
message: error.to_string(),
}
}
}
impl From&lt;num::ParseIntError&gt; for AppError {
fn from(error: num::ParseIntError) -&gt; Self {
AppError {
kind: String::from(&quot;parse&quot;),
message: error.to_string(),
}
}
}
fn main() -&gt; Result&lt;(), AppError&gt; {
let mut file = File::open(&quot;hello_world.txt&quot;)?;
let mut content = String::new();
file.read_to_string(&amp;mut content)?;
let _number: usize;
_number = content.parse()?;
Ok(())
}
// --------------- 上述代码运行后的可能输出 ---------------
// 01. 若 hello_world.txt 文件不存在
Error: AppError { kind: &quot;io&quot;, message: &quot;No such file or directory (os error 2)&quot; }
// 02. 若用户没有相关的权限访问 hello_world.txt
Error: AppError { kind: &quot;io&quot;, message: &quot;Permission denied (os error 13)&quot; }
// 03. 若 hello_world.txt 包含有非数字的内容，例如 Hello, world!
Error: AppError { kind: &quot;parse&quot;, message: &quot;invalid digit found in string&quot; }</code></pre></pre>
<h2 id="归一化不同的错误类型"><a class="header" href="#归一化不同的错误类型">归一化不同的错误类型</a></h2>
<p>至此，关于 Rust 的错误处理大家已经了若指掌了，下面再来看看一些实战中的问题。</p>
<p>在实际项目中，我们往往会为不同的错误定义不同的类型，这样做非常好，但是如果你要在一个函数中返回不同的错误呢？例如：</p>
<pre><pre class="playground"><code class="language-rust edition2021">use std::fs::read_to_string;
fn main() -&gt; Result&lt;(), std::io::Error&gt; {
let html = render()?;
println!(&quot;{}&quot;, html);
Ok(())
}
fn render() -&gt; Result&lt;String, std::io::Error&gt; {
let file = std::env::var(&quot;MARKDOWN&quot;)?;
let source = read_to_string(file)?;
Ok(source)
}</code></pre></pre>
<p>上面的代码会报错，原因在于 <code>render</code> 函数中的两个 <code>?</code> 返回的实际上是不同的错误：<code>env::var()</code> 返回的是 <code>std::env::VarError</code>，而 <code>read_to_string</code> 返回的是 <code>std::io::Error</code>。</p>
<p>为了满足 <code>render</code> 函数的签名，我们就需要将 <code>env::VarError</code> 和 <code>io::Error</code> 归一化为同一种错误类型。要实现这个目的有三种方式:</p>
<ul>
<li>使用特征对象 <code>Box&lt;dyn Error&gt;</code></li>
<li>自定义错误类型</li>
<li>使用 <code>thiserror</code></li>
</ul>
<p>下面依次来看看相关的解决方式。</p>
<h4 id="boxdyn-error"><a class="header" href="#boxdyn-error"><code>Box&lt;dyn Error&gt;</code></a></h4>
<p>大家还记得我们之前提到的 <code>std::error::Error</code> 特征吧，当时有说：自定义类型实现 <code>Debug + Display</code> 特征的主要原因就是为了能转换成 <code>Error</code> 的特征对象，而特征对象恰恰是在同一个地方使用不同类型的关键:</p>
<pre><pre class="playground"><code class="language-rust edition2021">use std::fs::read_to_string;
use std::error::Error;
fn main() -&gt; Result&lt;(), Box&lt;dyn Error&gt;&gt; {
let html = render()?;
println!(&quot;{}&quot;, html);
Ok(())
}
fn render() -&gt; Result&lt;String, Box&lt;dyn Error&gt;&gt; {
let file = std::env::var(&quot;MARKDOWN&quot;)?;
let source = read_to_string(file)?;
Ok(source)
}</code></pre></pre>
<p>这个方法很简单，在绝大多数场景中，性能也非常够用，但是有一个问题：<code>Result</code> 实际上不会限制错误的类型，也就是一个类型就算不实现 <code>Error</code> 特征，它依然可以在 <code>Result&lt;T, E&gt;</code> 中作为 <code>E</code> 来使用，此时这种特征对象的解决方案就无能为力了。</p>
<h4 id="自定义错误类型-1"><a class="header" href="#自定义错误类型-1">自定义错误类型</a></h4>
<p>与特征对象相比，自定义错误类型麻烦归麻烦，但是它非常灵活，因此也不具有上面的类似限制:</p>
<pre><pre class="playground"><code class="language-rust edition2021">use std::fs::read_to_string;
fn main() -&gt; Result&lt;(), MyError&gt; {
let html = render()?;
println!(&quot;{}&quot;, html);
Ok(())
}
fn render() -&gt; Result&lt;String, MyError&gt; {
let file = std::env::var(&quot;MARKDOWN&quot;)?;
let source = read_to_string(file)?;
Ok(source)
}
#[derive(Debug)]
enum MyError {
EnvironmentVariableNotFound,
IOError(std::io::Error),
}
impl From&lt;std::env::VarError&gt; for MyError {
fn from(_: std::env::VarError) -&gt; Self {
Self::EnvironmentVariableNotFound
}
}
impl From&lt;std::io::Error&gt; for MyError {
fn from(value: std::io::Error) -&gt; Self {
Self::IOError(value)
}
}
impl std::error::Error for MyError {}
impl std::fmt::Display for MyError {
fn fmt(&amp;self, f: &amp;mut std::fmt::Formatter&lt;'_&gt;) -&gt; std::fmt::Result {
match self {
MyError::EnvironmentVariableNotFound =&gt; write!(f, &quot;Environment variable not found&quot;),
MyError::IOError(err) =&gt; write!(f, &quot;IO Error: {}&quot;, err.to_string()),
}
}
}</code></pre></pre>
<p>上面代码中有一行值得注意：<code>impl std::error::Error for MyError {}</code> ，只有为自定义错误类型实现 <code>Error</code> 特征后，才能转换成相应的特征对象。</p>
<p>不得不说，真是啰嗦啊。因此在能用特征对象的时候，建议大家还是使用特征对象，无论如何，代码可读性还是很重要的！</p>
<p>上面的第二种方式灵活归灵活，啰嗦也是真啰嗦，好在 Rust 的社区为我们提供了 <code>thiserror</code> 解决方案，下面一起来看看该如何简化 Rust 中的错误处理。</p>
<h2 id="简化错误处理"><a class="header" href="#简化错误处理">简化错误处理</a></h2>
<p>对于开发者而言，错误处理是代码中打交道最多的部分之一，因此选择一把趁手的武器也很重要，它可以帮助我们节省大量的时间和精力，好钢应该用在代码逻辑而不是冗长的错误处理上。</p>
<h4 id="thiserror"><a class="header" href="#thiserror">thiserror</a></h4>
<p><a href="https://github.com/dtolnay/thiserror"><code>thiserror</code></a>可以帮助我们简化上面的第二种解决方案：</p>
<pre><pre class="playground"><code class="language-rust edition2021">use std::fs::read_to_string;
fn main() -&gt; Result&lt;(), MyError&gt; {
let html = render()?;
println!(&quot;{}&quot;, html);
Ok(())
}
fn render() -&gt; Result&lt;String, MyError&gt; {
let file = std::env::var(&quot;MARKDOWN&quot;)?;
let source = read_to_string(file)?;
Ok(source)
}
#[derive(thiserror::Error, Debug)]
enum MyError {
#[error(&quot;Environment variable not found&quot;)]
EnvironmentVariableNotFound(#[from] std::env::VarError),
#[error(transparent)]
IOError(#[from] std::io::Error),
}</code></pre></pre>
<p>如上所示，只要简单写写注释，就可以实现错误处理了，惊不惊喜？</p>
<h4 id="error-chain"><a class="header" href="#error-chain">error-chain</a></h4>
<p><a href="https://github.com/rust-lang-deprecated/error-chain"><code>error-chain</code></a> 也是简单好用的库，可惜不再维护了，但是我觉得它依然可以在合适的地方大放光彩，值得大家去了解下。</p>
<pre><pre class="playground"><code class="language-rust edition2021">use std::fs::read_to_string;
error_chain::error_chain! {
foreign_links {
EnvironmentVariableNotFound(::std::env::VarError);
IOError(::std::io::Error);
}
}
fn main() -&gt; Result&lt;()&gt; {
let html = render()?;
println!(&quot;{}&quot;, html);
Ok(())
}
fn render() -&gt; Result&lt;String&gt; {
let file = std::env::var(&quot;MARKDOWN&quot;)?;
let source = read_to_string(file)?;
Ok(source)
}</code></pre></pre>
<p>喏，简单吧？使用 <code>error-chain</code> 的宏你可以获得：<code>Error</code> 结构体，错误类型 <code>ErrorKind</code> 枚举 以及一个自定义的 <code>Result</code> 类型。</p>
<h4 id="anyhow"><a class="header" href="#anyhow">anyhow</a></h4>
<p><a href="https://github.com/dtolnay/anyhow"><code>anyhow</code></a> 和 <code>thiserror</code> 是同一个作者开发的，这里是作者关于 <code>anyhow</code> 和 <code>thiserror</code> 的原话：</p>
<blockquote>
<p>如果你想要设计自己的错误类型，同时给调用者提供具体的信息时，就使用 <code>thiserror</code>，例如当你在开发一个三方库代码时。如果你只想要简单，就使用 <code>anyhow</code>，例如在自己的应用服务中。</p>
</blockquote>
<pre><pre class="playground"><code class="language-rust edition2021">use std::fs::read_to_string;
use anyhow::Result;
fn main() -&gt; Result&lt;()&gt; {
let html = render()?;
println!(&quot;{}&quot;, html);
Ok(())
}
fn render() -&gt; Result&lt;String&gt; {
let file = std::env::var(&quot;MARKDOWN&quot;)?;
let source = read_to_string(file)?;
Ok(source)
}</code></pre></pre>
<p>关于如何选用 <code>thiserror</code> 和 <code>anyhow</code> 只需要遵循一个原则即可：<strong>是否关注自定义错误消息</strong>，关注则使用 <code>thiserror</code>（常见业务代码），否则使用 <code>anyhow</code>（编写第三方库代码）。</p>
<h2 id="总结"><a class="header" href="#总结">总结</a></h2>
<p>Rust 一个为人津津乐道的点就是强大、易用的错误处理，对于新手来说，这个机制可能会有些复杂，但是一旦体会到了其中的好处，你将跟我一样沉醉其中不能自拔。</p>
<div id="giscus-container"></div>
</main>
<nav class="nav-wrapper" aria-label="Page navigation">
<!-- Mobile navigation buttons -->
<a rel="prev" href="../advance/global-variable.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
<i class="fa fa-angle-left"></i>
</a>
<a rel="next prefetch" href="../advance/unsafe/intro.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
<i class="fa fa-angle-right"></i>
</a>
<div style="clear: both"></div>
</nav>
</div>
</div>
<nav class="nav-wide-wrapper" aria-label="Page navigation">
<a rel="prev" href="../advance/global-variable.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
<i class="fa fa-angle-left"></i>
</a>
<a rel="next prefetch" href="../advance/unsafe/intro.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
<i class="fa fa-angle-right"></i>
</a>
</nav>
</div>
<script>
window.playground_copyable = true;
</script>
<script src="../ace.js"></script>
<script src="../editor.js"></script>
<script src="../mode-rust.js"></script>
<script src="../theme-dawn.js"></script>
<script src="../theme-tomorrow_night.js"></script>
<script src="../elasticlunr.min.js"></script>
<script src="../mark.min.js"></script>
<script src="../searcher.js"></script>
<script src="../clipboard.min.js"></script>
<script src="../highlight.js"></script>
<script src="../book.js"></script>
<script type="text/javascript" charset="utf-8">
var pagePath = "advance/errors.md"
</script>
<!-- Custom JS scripts -->
<script src="../assets/custom.js"></script>
<script src="../assets/bigPicture.js"></script>
</div>
</body>
</html>
Reference in new issue View Git Blame Copy Permalink