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<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 expanded "><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 expanded "><a href="../../advance/functional-programing/iterator.html" class="active"><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 "><a href="../../advance/errors.html"><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 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<main>
<h1 id="迭代器-iterator"><a class="header" href="#迭代器-iterator">迭代器 Iterator</a></h1>
<p>如果你询问一个 Rust 资深开发：写 Rust 项目最需要掌握什么？相信迭代器往往就是答案之一。无论你是编程新手亦或是高手，实际上大概率都用过迭代器，虽然自己可能并没有意识到这一点:)</p>
<p>迭代器允许我们迭代一个连续的集合，例如数组、动态数组 <code>Vec</code>、<code>HashMap</code> 等，在此过程中，只需关心集合中的元素如何处理，而无需关心如何开始、如何结束、按照什么样的索引去访问等问题。</p>
<h2 id="for-循环与迭代器"><a class="header" href="#for-循环与迭代器">For 循环与迭代器</a></h2>
<p>从用途来看，迭代器跟 <code>for</code> 循环颇为相似，都是去遍历一个集合，但是实际上它们存在不小的差别，其中最主要的差别就是：<strong>是否通过索引来访问集合</strong>。</p>
<p>例如以下的 JS 代码就是一个循环：</p>
<pre><code class="language-javascript">let arr = [1, 2, 3];
for (let i = 0; i &lt; arr.length; i++) {
console.log(arr[i]);
}
</code></pre>
<p>在上面代码中，我们设置索引的开始点和结束点，然后再通过索引去访问元素 <code>arr[i]</code>，这就是典型的循环，来对比下 Rust 中的 <code>for</code>：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let arr = [1, 2, 3];
for v in arr {
println!(&quot;{}&quot;,v);
}
<span class="boring">}</span></code></pre></pre>
<p>首先，不得不说这两语法还挺像！与 JS 循环不同，<code>Rust</code>中没有使用索引，它把 <code>arr</code> 数组当成一个迭代器，直接去遍历其中的元素，从哪里开始，从哪里结束，都无需操心。因此严格来说，Rust 中的 <code>for</code> 循环是编译器提供的语法糖，最终还是对迭代器中的元素进行遍历。</p>
<p>那又有同学要发问了，在 Rust 中数组是迭代器吗？因为在之前的代码中直接对数组 <code>arr</code> 进行了迭代，答案是 <code>No</code>。那既然数组不是迭代器，为啥咱可以对它的元素进行迭代呢？</p>
<p>简而言之就是数组实现了 <code>IntoIterator</code> 特征，Rust 通过 <code>for</code> 语法糖，自动把实现了该特征的数组类型转换为迭代器（你也可以为自己的集合类型实现此特征），最终让我们可以直接对一个数组进行迭代，类似的还有：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>for i in 1..10 {
println!(&quot;{}&quot;, i);
}
<span class="boring">}</span></code></pre></pre>
<p>直接对数值序列进行迭代，也是很常见的使用方式。</p>
<p><code>IntoIterator</code> 特征拥有一个 <code>into_iter</code> 方法，因此我们还可以显式的把数组转换成迭代器：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let arr = [1, 2, 3];
for v in arr.into_iter() {
println!(&quot;{}&quot;, v);
}
<span class="boring">}</span></code></pre></pre>
<p>迭代器是函数语言的核心特性，它赋予了 Rust 远超于循环的强大表达能力，我们将在本章中一一为大家进行展现。</p>
<h2 id="惰性初始化"><a class="header" href="#惰性初始化">惰性初始化</a></h2>
<p>在 Rust 中，迭代器是惰性的，意味着如果你不使用它，那么它将不会发生任何事：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let v1 = vec![1, 2, 3];
let v1_iter = v1.iter();
for val in v1_iter {
println!(&quot;{}&quot;, val);
}
<span class="boring">}</span></code></pre></pre>
<p>在 <code>for</code> 循环之前，我们只是简单的创建了一个迭代器 <code>v1_iter</code>，此时不会发生任何迭代行为，只有在 <code>for</code> 循环开始后，迭代器才会开始迭代其中的元素，最后打印出来。</p>
<p>这种惰性初始化的方式确保了创建迭代器不会有任何额外的性能损耗，其中的元素也不会被消耗，只有使用到该迭代器的时候，一切才开始。</p>
<h2 id="next-方法"><a class="header" href="#next-方法">next 方法</a></h2>
<p>对于 <code>for</code> 如何遍历迭代器，还有一个问题，它如何取出迭代器中的元素？</p>
<p>先来看一个特征：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub trait Iterator {
type Item;
fn next(&amp;mut self) -&gt; Option&lt;Self::Item&gt;;
// 省略其余有默认实现的方法
}
<span class="boring">}</span></code></pre></pre>
<p>呦，该特征竟然和迭代器 <code>iterator</code> 同名，难不成。。。没错，它们就是有一腿。<strong>迭代器之所以成为迭代器，就是因为实现了 <code>Iterator</code> 特征</strong>，要实现该特征，最主要的就是实现其中的 <code>next</code> 方法，该方法控制如何从集合中取值，最终返回值的类型是<a href="https://course.rs/basic/trait/advance-trait#%E5%85%B3%E8%81%94%E7%B1%BB%E5%9E%8B">关联类型</a> <code>Item</code>。</p>
<p>因此，之前问题的答案已经很明显：<code>for</code> 循环通过不停调用迭代器上的 <code>next</code> 方法，来获取迭代器中的元素。</p>
<p>既然 <code>for</code> 可以调用 <code>next</code> 方法，是不是意味着我们也可以？来试试：</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
let arr = [1, 2, 3];
let mut arr_iter = arr.into_iter();
assert_eq!(arr_iter.next(), Some(1));
assert_eq!(arr_iter.next(), Some(2));
assert_eq!(arr_iter.next(), Some(3));
assert_eq!(arr_iter.next(), None);
}</code></pre></pre>
<p>果不其然，将 <code>arr</code> 转换成迭代器后，通过调用其上的 <code>next</code> 方法，我们获取了 <code>arr</code> 中的元素，有两点需要注意：</p>
<ul>
<li><code>next</code> 方法返回的是 <code>Option</code> 类型，当有值时返回 <code>Some(i32)</code>，无值时返回 <code>None</code></li>
<li>遍历是按照迭代器中元素的排列顺序依次进行的，因此我们严格按照数组中元素的顺序取出了 <code>Some(1)</code>，<code>Some(2)</code>，<code>Some(3)</code></li>
<li>手动迭代必须将迭代器声明为 <code>mut</code> 可变，因为调用 <code>next</code> 会改变迭代器其中的状态数据（当前遍历的位置等），而 <code>for</code> 循环去迭代则无需标注 <code>mut</code>，因为它会帮我们自动完成</li>
</ul>
<p>总之，<code>next</code> 方法对<strong>迭代器的遍历是消耗性的</strong>，每次消耗它一个元素，最终迭代器中将没有任何元素，只能返回 <code>None</code>。</p>
<h4 id="例子模拟实现-for-循环"><a class="header" href="#例子模拟实现-for-循环">例子：模拟实现 for 循环</a></h4>
<p>因为 <code>for</code> 循环是迭代器的语法糖，因此我们完全可以通过迭代器来模拟实现它：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let values = vec![1, 2, 3];
{
let result = match IntoIterator::into_iter(values) {
mut iter =&gt; loop {
match iter.next() {
Some(x) =&gt; { println!(&quot;{}&quot;, x); },
None =&gt; break,
}
},
};
result
}
<span class="boring">}</span></code></pre></pre>
<p><code>IntoIterator::into_iter</code> 是使用<a href="https://course.rs/basic/trait/advance-trait.html#%E5%AE%8C%E5%85%A8%E9%99%90%E5%AE%9A%E8%AF%AD%E6%B3%95">完全限定</a>的方式去调用 <code>into_iter</code> 方法，这种调用方式跟 <code>values.into_iter()</code> 是等价的。</p>
<p>同时我们使用了 <code>loop</code> 循环配合 <code>next</code> 方法来遍历迭代器中的元素，当迭代器返回 <code>None</code> 时，跳出循环。</p>
<h2 id="intoiterator-特征"><a class="header" href="#intoiterator-特征">IntoIterator 特征</a></h2>
<p>其实有一个细节，由于 <code>Vec</code> 动态数组实现了 <code>IntoIterator</code> 特征，因此可以通过 <code>into_iter</code> 将其转换为迭代器，那如果本身就是一个迭代器，该怎么办？实际上，迭代器自身也实现了 <code>IntoIterator</code>，标准库早就帮我们考虑好了：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>impl&lt;I: Iterator&gt; IntoIterator for I {
type Item = I::Item;
type IntoIter = I;
#[inline]
fn into_iter(self) -&gt; I {
self
}
}
<span class="boring">}</span></code></pre></pre>
<p>最终你完全可以写出这样的奇怪代码：</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
let values = vec![1, 2, 3];
for v in values.into_iter().into_iter().into_iter() {
println!(&quot;{}&quot;,v)
}
}</code></pre></pre>
<h4 id="into_iter-iter-iter_mut"><a class="header" href="#into_iter-iter-iter_mut">into_iter, iter, iter_mut</a></h4>
<p>在之前的代码中，我们统一使用了 <code>into_iter</code> 的方式将数组转化为迭代器，除此之外，还有 <code>iter</code> 和 <code>iter_mut</code>，聪明的读者应该大概能猜到这三者的区别：</p>
<ul>
<li><code>into_iter</code> 会夺走所有权</li>
<li><code>iter</code> 是借用</li>
<li><code>iter_mut</code> 是可变借用</li>
</ul>
<p>其实如果以后见多识广了，你会发现这种问题一眼就能看穿，<code>into_</code> 之类的，都是拿走所有权，<code>_mut</code> 之类的都是可变借用，剩下的就是不可变借用。</p>
<p>使用一段代码来解释下：</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
let values = vec![1, 2, 3];
for v in values.into_iter() {
println!(&quot;{}&quot;, v)
}
// 下面的代码将报错，因为 values 的所有权在上面 `for` 循环中已经被转移走
// println!(&quot;{:?}&quot;,values);
let values = vec![1, 2, 3];
let _values_iter = values.iter();
// 不会报错，因为 values_iter 只是借用了 values 中的元素
println!(&quot;{:?}&quot;, values);
let mut values = vec![1, 2, 3];
// 对 values 中的元素进行可变借用
let mut values_iter_mut = values.iter_mut();
// 取出第一个元素，并修改为0
if let Some(v) = values_iter_mut.next() {
*v = 0;
}
// 输出[0, 2, 3]
println!(&quot;{:?}&quot;, values);
}</code></pre></pre>
<p>具体解释在代码注释中，就不再赘述，不过有两点需要注意的是：</p>
<ul>
<li><code>.iter()</code> 方法实现的迭代器，调用 <code>next</code> 方法返回的类型是 <code>Some(&amp;T)</code></li>
<li><code>.iter_mut()</code> 方法实现的迭代器，调用 <code>next</code> 方法返回的类型是 <code>Some(&amp;mut T)</code>，因此在 <code>if let Some(v) = values_iter_mut.next()</code> 中，<code>v</code> 的类型是 <code>&amp;mut i32</code>，最终我们可以通过 <code>*v = 0</code> 的方式修改其值</li>
</ul>
<h4 id="iterator-和-intoiterator-的区别"><a class="header" href="#iterator-和-intoiterator-的区别">Iterator 和 IntoIterator 的区别</a></h4>
<p>这两个其实还蛮容易搞混的，但我们只需要记住，<code>Iterator</code> 就是迭代器特征，只有实现了它才能称为迭代器，才能调用 <code>next</code>。</p>
<p>而 <code>IntoIterator</code> 强调的是某一个类型如果实现了该特征，它可以通过 <code>into_iter</code>，<code>iter</code> 等方法变成一个迭代器。</p>
<h2 id="消费者与适配器"><a class="header" href="#消费者与适配器">消费者与适配器</a></h2>
<p>消费者是迭代器上的方法，它会消费掉迭代器中的元素，然后返回其类型的值，这些消费者都有一个共同的特点：在它们的定义中，都依赖 <code>next</code> 方法来消费元素，因此这也是为什么迭代器要实现 <code>Iterator</code> 特征，而该特征必须要实现 <code>next</code> 方法的原因。</p>
<h4 id="消费者适配器"><a class="header" href="#消费者适配器">消费者适配器</a></h4>
<p>只要迭代器上的某个方法 <code>A</code> 在其内部调用了 <code>next</code> 方法，那么 <code>A</code> 就被称为<strong>消费性适配器</strong>：因为 <code>next</code> 方法会消耗掉迭代器上的元素，所以方法 <code>A</code> 的调用也会消耗掉迭代器上的元素。</p>
<p>其中一个例子是 <code>sum</code> 方法，它会拿走迭代器的所有权，然后通过不断调用 <code>next</code> 方法对里面的元素进行求和：</p>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
let v1 = vec![1, 2, 3];
let v1_iter = v1.iter();
let total: i32 = v1_iter.sum();
assert_eq!(total, 6);
// v1_iter 是借用了 v1，因此 v1 可以照常使用
println!(&quot;{:?}&quot;,v1);
// 以下代码会报错，因为 `sum` 拿到了迭代器 `v1_iter` 的所有权
// println!(&quot;{:?}&quot;,v1_iter);
}</code></pre></pre>
<p>如代码注释中所说明的：在使用 <code>sum</code> 方法后，我们将无法再使用 <code>v1_iter</code>，因为 <code>sum</code> 拿走了该迭代器的所有权：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>fn sum&lt;S&gt;(self) -&gt; S
where
Self: Sized,
S: Sum&lt;Self::Item&gt;,
{
Sum::sum(self)
}
<span class="boring">}</span></code></pre></pre>
<p>从 <code>sum</code> 源码中也可以清晰看出，<code>self</code> 类型的方法参数拿走了所有权。</p>
<h4 id="迭代器适配器"><a class="header" href="#迭代器适配器">迭代器适配器</a></h4>
<p>既然消费者适配器是消费掉迭代器，然后返回一个值。那么迭代器适配器，顾名思义，会返回一个新的迭代器，这是实现链式方法调用的关键：<code>v.iter().map().filter()...</code>。</p>
<p>与消费者适配器不同，迭代器适配器是惰性的，意味着你<strong>需要一个消费者适配器来收尾，最终将迭代器转换成一个具体的值</strong>：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let v1: Vec&lt;i32&gt; = vec![1, 2, 3];
v1.iter().map(|x| x + 1);
<span class="boring">}</span></code></pre></pre>
<p>运行后输出:</p>
<pre><code class="language-console">warning: unused `Map` that must be used
--&gt; src/main.rs:4:5
|
4 | v1.iter().map(|x| x + 1);
| ^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `#[warn(unused_must_use)]` on by default
= note: iterators are lazy and do nothing unless consumed // 迭代器 map 是惰性的，这里不产生任何效果
</code></pre>
<p>如上述中文注释所说，这里的 <code>map</code> 方法是一个迭代者适配器，它是惰性的，不产生任何行为，因此我们还需要一个消费者适配器进行收尾：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let v1: Vec&lt;i32&gt; = vec![1, 2, 3];
let v2: Vec&lt;_&gt; = v1.iter().map(|x| x + 1).collect();
assert_eq!(v2, vec![2, 3, 4]);
<span class="boring">}</span></code></pre></pre>
<h4 id="collect"><a class="header" href="#collect">collect</a></h4>
<p>上面代码中，使用了 <code>collect</code> 方法，该方法就是一个消费者适配器，使用它可以将一个迭代器中的元素收集到指定类型中，这里我们为 <code>v2</code> 标注了 <code>Vec&lt;_&gt;</code> 类型，就是为了告诉 <code>collect</code>：请把迭代器中的元素消费掉，然后把值收集成 <code>Vec&lt;_&gt;</code> 类型，至于为何使用 <code>_</code>，因为编译器会帮我们自动推导。</p>
<p>为何 <code>collect</code> 在消费时要指定类型？是因为该方法其实很强大，可以收集成多种不同的集合类型，<code>Vec&lt;T&gt;</code> 仅仅是其中之一，因此我们必须显式的告诉编译器我们想要收集成的集合类型。</p>
<p>还有一点值得注意，<code>map</code> 会对迭代器中的每一个值进行一系列操作，然后把该值转换成另外一个新值，该操作是通过闭包 <code>|x| x + 1</code> 来完成：最终迭代器中的每个值都增加了 <code>1</code>，从 <code>[1, 2, 3]</code> 变为 <code>[2, 3, 4]</code>。</p>
<p>再来看看如何使用 <code>collect</code> 收集成 <code>HashMap</code> 集合：</p>
<pre><pre class="playground"><code class="language-rust edition2021">use std::collections::HashMap;
fn main() {
let names = [&quot;sunface&quot;, &quot;sunfei&quot;];
let ages = [18, 18];
let folks: HashMap&lt;_, _&gt; = names.into_iter().zip(ages.into_iter()).collect();
println!(&quot;{:?}&quot;,folks);
}</code></pre></pre>
<p><code>zip</code> 是一个迭代器适配器，它的作用就是将两个迭代器的内容压缩到一起，形成 <code>Iterator&lt;Item=(ValueFromA, ValueFromB)&gt;</code> 这样的新的迭代器，在此处就是形如 <code>[(name1, age1), (name2, age2)]</code> 的迭代器。</p>
<p>然后再通过 <code>collect</code> 将新迭代器中<code>(K, V)</code> 形式的值收集成 <code>HashMap&lt;K, V&gt;</code>，同样的，这里必须显式声明类型，然后 <code>HashMap</code> 内部的 <code>KV</code> 类型可以交给编译器去推导，最终编译器会推导出 <code>HashMap&lt;&amp;str, i32&gt;</code>，完全正确！</p>
<h4 id="闭包作为适配器参数"><a class="header" href="#闭包作为适配器参数">闭包作为适配器参数</a></h4>
<p>之前的 <code>map</code> 方法中，我们使用闭包来作为迭代器适配器的参数，它最大的好处不仅在于可以就地实现迭代器中元素的处理，还在于可以捕获环境值：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>struct Shoe {
size: u32,
style: String,
}
fn shoes_in_size(shoes: Vec&lt;Shoe&gt;, shoe_size: u32) -&gt; Vec&lt;Shoe&gt; {
shoes.into_iter().filter(|s| s.size == shoe_size).collect()
}
<span class="boring">}</span></code></pre></pre>
<p><code>filter</code> 是迭代器适配器，用于对迭代器中的每个值进行过滤。 它使用闭包作为参数，该闭包的参数 <code>s</code> 是来自迭代器中的值，然后使用 <code>s</code> 跟外部环境中的 <code>shoe_size</code> 进行比较，若相等，则在迭代器中保留 <code>s</code> 值，若不相等，则从迭代器中剔除 <code>s</code> 值，最终通过 <code>collect</code> 收集为 <code>Vec&lt;Shoe&gt;</code> 类型。</p>
<h2 id="实现-iterator-特征"><a class="header" href="#实现-iterator-特征">实现 Iterator 特征</a></h2>
<p>之前的内容我们一直基于数组来创建迭代器，实际上，不仅仅是数组，基于其它集合类型一样可以创建迭代器，例如 <code>HashMap</code>。 你也可以创建自己的迭代器 —— 只要为自定义类型实现 <code>Iterator</code> 特征即可。</p>
<p>首先，创建一个计数器：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>struct Counter {
count: u32,
}
impl Counter {
fn new() -&gt; Counter {
Counter { count: 0 }
}
}
<span class="boring">}</span></code></pre></pre>
<p>我们为计数器 <code>Counter</code> 实现了一个关联函数 <code>new</code>，用于创建新的计数器实例。下面我们继续为计数器实现 <code>Iterator</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>impl Iterator for Counter {
type Item = u32;
fn next(&amp;mut self) -&gt; Option&lt;Self::Item&gt; {
if self.count &lt; 5 {
self.count += 1;
Some(self.count)
} else {
None
}
}
}
<span class="boring">}</span></code></pre></pre>
<p>首先，将该特征的关联类型设置为 <code>u32</code>，由于我们的计数器保存的 <code>count</code> 字段就是 <code>u32</code> 类型， 因此在 <code>next</code> 方法中，最后返回的是实际上是 <code>Option&lt;u32&gt;</code> 类型。</p>
<p>每次调用 <code>next</code> 方法，都会让计数器的值加一，然后返回最新的计数值，一旦计数大于 5，就返回 <code>None</code>。</p>
<p>最后，使用我们新建的 <code>Counter</code> 进行迭代：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span> let mut counter = Counter::new();
assert_eq!(counter.next(), Some(1));
assert_eq!(counter.next(), Some(2));
assert_eq!(counter.next(), Some(3));
assert_eq!(counter.next(), Some(4));
assert_eq!(counter.next(), Some(5));
assert_eq!(counter.next(), None);
<span class="boring">}</span></code></pre></pre>
<h4 id="实现-iterator-特征的其它方法"><a class="header" href="#实现-iterator-特征的其它方法">实现 Iterator 特征的其它方法</a></h4>
<p>可以看出，实现自己的迭代器非常简单，但是 <code>Iterator</code> 特征中，不仅仅是只有 <code>next</code> 一个方法，那为什么我们只需要实现它呢？因为其它方法都具有<a href="https://course.rs/basic/trait/trait.html#%E9%BB%98%E8%AE%A4%E5%AE%9E%E7%8E%B0">默认实现</a>，所以无需像 <code>next</code> 这样手动去实现，而且这些默认实现的方法其实都是基于 <code>next</code> 方法实现的。</p>
<p>下面的代码演示了部分方法的使用：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let sum: u32 = Counter::new()
.zip(Counter::new().skip(1))
.map(|(a, b)| a * b)
.filter(|x| x % 3 == 0)
.sum();
assert_eq!(18, sum);
<span class="boring">}</span></code></pre></pre>
<p>其中 <code>zip</code>，<code>map</code>，<code>filter</code> 是迭代器适配器：</p>
<ul>
<li><code>zip</code> 把两个迭代器合并成一个迭代器，新迭代器中，每个元素都是一个元组，由之前两个迭代器的元素组成。例如将<strong>形如</strong> <code>[1, 2, 3, 4, 5]</code> 和 <code>[2, 3, 4, 5]</code> 的迭代器合并后，新的迭代器形如 <code>[(1, 2),(2, 3),(3, 4),(4, 5)]</code></li>
<li><code>map</code> 是将迭代器中的值经过映射后，转换成新的值[2, 6, 12, 20]</li>
<li><code>filter</code> 对迭代器中的元素进行过滤，若闭包返回 <code>true</code> 则保留元素[6, 12]，反之剔除</li>
</ul>
<p>而 <code>sum</code> 是消费者适配器，对迭代器中的所有元素求和，最终返回一个 <code>u32</code> 值 <code>18</code>。</p>
<h5 id="enumerate"><a class="header" href="#enumerate">enumerate</a></h5>
<p>在之前的流程控制章节，针对 <code>for</code> 循环，我们提供了一种方法可以获取迭代时的索引：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let v = vec![1u64, 2, 3, 4, 5, 6];
for (i,v) in v.iter().enumerate() {
println!(&quot;第{}个值是{}&quot;,i,v)
}
<span class="boring">}</span></code></pre></pre>
<p>相信当时，很多读者还是很迷茫的，不知道为什么要这么复杂才能获取到索引，学习本章节后，相信你有了全新的理解，首先 <code>v.iter()</code> 创建迭代器，其次
调用 <code>Iterator</code> 特征上的方法 <code>enumerate</code>，该方法产生一个新的迭代器，其中每个元素均是元组 <code>(索引，值)</code>。</p>
<p>因为 <code>enumerate</code> 是迭代器适配器，因此我们可以对它返回的迭代器调用其它 <code>Iterator</code> 特征方法：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let v = vec![1u64, 2, 3, 4, 5, 6];
let val = v.iter()
.enumerate()
// 每两个元素剔除一个
// [1, 3, 5]
.filter(|&amp;(idx, _)| idx % 2 == 0)
.map(|(_, val)| val)
// 累加 1+3+5 = 9
.fold(0u64, |sum, acm| sum + acm);
println!(&quot;{}&quot;, val);
<span class="boring">}</span></code></pre></pre>
<h2 id="迭代器的性能"><a class="header" href="#迭代器的性能">迭代器的性能</a></h2>
<p>前面提到，要完成集合遍历，既可以使用 <code>for</code> 循环也可以使用迭代器，那么二者之间该怎么选择呢，性能有多大差距呢？</p>
<p>理论分析不会有结果，直接测试最为靠谱：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span>#![feature(test)]
<span class="boring">fn main() {
</span>extern crate rand;
extern crate test;
fn sum_for(x: &amp;[f64]) -&gt; f64 {
let mut result: f64 = 0.0;
for i in 0..x.len() {
result += x[i];
}
result
}
fn sum_iter(x: &amp;[f64]) -&gt; f64 {
x.iter().sum::&lt;f64&gt;()
}
#[cfg(test)]
mod bench {
use test::Bencher;
use rand::{Rng,thread_rng};
use super::*;
const LEN: usize = 1024*1024;
fn rand_array(cnt: u32) -&gt; Vec&lt;f64&gt; {
let mut rng = thread_rng();
(0..cnt).map(|_| rng.gen::&lt;f64&gt;()).collect()
}
#[bench]
fn bench_for(b: &amp;mut Bencher) {
let samples = rand_array(LEN as u32);
b.iter(|| {
sum_for(&amp;samples)
})
}
#[bench]
fn bench_iter(b: &amp;mut Bencher) {
let samples = rand_array(LEN as u32);
b.iter(|| {
sum_iter(&amp;samples)
})
}
}
<span class="boring">}</span></code></pre></pre>
<p>上面的代码对比了 <code>for</code> 循环和迭代器 <code>iterator</code> 完成同样的求和任务的性能对比，可以看到迭代器还要更快一点。</p>
<pre><code class="language-console">test bench::bench_for ... bench: 998,331 ns/iter (+/- 36,250)
test bench::bench_iter ... bench: 983,858 ns/iter (+/- 44,673)
</code></pre>
<p>迭代器是 Rust 的 <strong>零成本抽象</strong>（zero-cost abstractions）之一，意味着抽象并不会引入运行时开销，这与 <code>Bjarne Stroustrup</code>（C++ 的设计和实现者）在 <code>Foundations of C++（2012）</code> 中所定义的 <strong>零开销</strong>（zero-overhead）如出一辙：</p>
<blockquote>
<p>In general, C++ implementations obey the zero-overhead principle: What you don’t use, you don’t pay for.
And further: What you do use, you couldn’t hand code any better.</p>
<p>一般来说，C++的实现遵循零开销原则：没有使用时，你不必为其买单。
更进一步说，需要使用时，你也无法写出更优的代码了。
（翻译一下：用就完事了）</p>
</blockquote>
<p>总之，迭代器是 Rust 受函数式语言启发而提供的高级语言特性，可以写出更加简洁、逻辑清晰的代码。编译器还可以通过循环展开（Unrolling）、向量化、消除边界检查等优化手段，使得迭代器和 <code>for</code> 循环都有极为高效的执行效率。</p>
<p>所以请放心大胆的使用迭代器，在获得更高的表达力的同时，也不会导致运行时的损失，何乐而不为呢！</p>
<h2 id="学习其它方法"><a class="header" href="#学习其它方法">学习其它方法</a></h2>
<p>迭代器用的好不好，就在于你是否掌握了它的常用方法，且能活学活用，因此多多看看<a href="https://doc.rust-lang.org/std/iter/trait.Iterator.html">标准库</a>是有好处的，只有知道有什么方法，在需要的时候你才能知道该用什么，就和算法学习一样。</p>
<p>同时，本书在后续章节还提供了对迭代器常用方法的<a href="https://course.rs/std/iterator">深入讲解</a>，方便大家学习和查阅。</p>
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