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<ol class="chapter"><li class="chapter-item expanded affix "><a href="title-page.html">Rust 程序设计语言</a></li><li class="chapter-item expanded affix "><a href="foreword.html">前言</a></li><li class="chapter-item expanded affix "><a href="ch00-00-introduction.html">简介</a></li><li class="chapter-item expanded "><a href="ch01-00-getting-started.html"><strong aria-hidden="true">1.</strong> 入门指南</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch01-01-installation.html"><strong aria-hidden="true">1.1.</strong> 安装</a></li><li class="chapter-item expanded "><a href="ch01-02-hello-world.html"><strong aria-hidden="true">1.2.</strong> Hello, World!</a></li><li class="chapter-item expanded "><a href="ch01-03-hello-cargo.html"><strong aria-hidden="true">1.3.</strong> Hello, Cargo!</a></li></ol></li><li class="chapter-item expanded "><a href="ch02-00-guessing-game-tutorial.html"><strong aria-hidden="true">2.</strong> 写个猜数字游戏</a></li><li class="chapter-item expanded "><a href="ch03-00-common-programming-concepts.html"><strong aria-hidden="true">3.</strong> 常见编程概念</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch03-01-variables-and-mutability.html"><strong aria-hidden="true">3.1.</strong> 变量与可变性</a></li><li class="chapter-item expanded "><a href="ch03-02-data-types.html"><strong aria-hidden="true">3.2.</strong> 数据类型</a></li><li class="chapter-item expanded "><a href="ch03-03-how-functions-work.html"><strong aria-hidden="true">3.3.</strong> 函数</a></li><li class="chapter-item expanded "><a href="ch03-04-comments.html"><strong aria-hidden="true">3.4.</strong> 注释</a></li><li class="chapter-item expanded "><a href="ch03-05-control-flow.html"><strong aria-hidden="true">3.5.</strong> 控制流</a></li></ol></li><li class="chapter-item expanded "><a href="ch04-00-understanding-ownership.html"><strong aria-hidden="true">4.</strong> 认识所有权</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch04-01-what-is-ownership.html"><strong aria-hidden="true">4.1.</strong> 什么是所有权?</a></li><li class="chapter-item expanded "><a href="ch04-02-references-and-borrowing.html"><strong aria-hidden="true">4.2.</strong> 引用与借用</a></li><li class="chapter-item expanded "><a href="ch04-03-slices.html"><strong aria-hidden="true">4.3.</strong> Slice 类型</a></li></ol></li><li class="chapter-item expanded "><a href="ch05-00-structs.html"><strong aria-hidden="true">5.</strong> 使用结构体组织相关联的数据</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch05-01-defining-structs.html"><strong aria-hidden="true">5.1.</strong> 结构体的定义和实例化</a></li><li class="chapter-item expanded "><a href="ch05-02-example-structs.html"><strong aria-hidden="true">5.2.</strong> 结构体示例程序</a></li><li class="chapter-item expanded "><a href="ch05-03-method-syntax.html"><strong aria-hidden="true">5.3.</strong> 方法语法</a></li></ol></li><li class="chapter-item expanded "><a href="ch06-00-enums.html"><strong aria-hidden="true">6.</strong> 枚举和模式匹配</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch06-01-defining-an-enum.html"><strong aria-hidden="true">6.1.</strong> 枚举的定义</a></li><li class="chapter-item expanded "><a href="ch06-02-match.html"><strong aria-hidden="true">6.2.</strong> match 控制流结构</a></li><li class="chapter-item expanded "><a href="ch06-03-if-let.html"><strong aria-hidden="true">6.3.</strong> if let 简洁控制流</a></li></ol></li><li class="chapter-item expanded "><a href="ch07-00-managing-growing-projects-with-packages-crates-and-modules.html"><strong aria-hidden="true">7.</strong> 使用包、Crate 和模块管理不断增长的项目</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="ch07-01-packages-and-crates.html" class="active"><strong aria-hidden="true">7.1.</strong> 包和 Crate</a></li><li class="chapter-item
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<h2 id="包和-crate"><a class="header" href="#包和-crate">包和 Crate</a></h2>
<blockquote>
<p><a href="https://github.com/rust-lang/book/blob/main/src/ch07-01-packages-and-crates.md">ch07-01-packages-and-crates.md</a>
<br>
commit c77d7a1279dbc7a9d76e80c5ac9d742dd529538c</p>
</blockquote>
<p>模块系统的第一部分,我们将介绍包和 crate。</p>
<p>crate 是 Rust 在编译时最小的代码单位。如果你用 <code>rustc</code> 而不是 <code>cargo</code> 来编译一个文件(第一章我们这么做过),编译器还是会将那个文件认作一个 crate。crate 可以包含模块,模块可以定义在其他文件,然后和 crate 一起编译,我们会在接下来的章节中遇到。</p>
<p>crate 有两种形式:二进制项和库。<em>二进制项</em> 可以被编译为可执行程序,比如一个命令行程序或者一个 web server。它们必须有一个 <code>main</code> 函数来定义当程序被执行的时候所需要做的事情。目前我们所创建的 crate 都是二进制项。</p>
<p><em></em> 并没有 <code>main</code> 函数,它们也不会编译为可执行程序,它们提供一些诸如函数之类的东西,使其他项目也能使用这些东西。比如 <a href="ch02-00-guessing-game-tutorial.html#%E7%94%9F%E6%88%90%E4%B8%80%E4%B8%AA%E9%9A%8F%E6%9C%BA%E6%95%B0">第二章</a><code>rand</code> crate 就提供了生成随机数的东西。大多数时间 <code>Rustaceans</code> 说的 crate 指的都是库,这与其他编程语言中 library 概念一致。</p>
<p><em>crate root</em> 是一个源文件Rust 编译器以它为起始点,并构成你的 crate 的根模块(我们将在 <a href="ch07-02-defining-modules-to-control-scope-and-privacy.html">“定义模块来控制作用域与私有性”</a> 一节深入解读)。</p>
<p><em></em><em>package</em>)是提供一系列功能的一个或者多个 crate。一个包会包含一个 <em>Cargo.toml</em> 文件,阐述如何去构建这些 crate。Cargo 就是一个包含构建你代码的二进制项的包。Cargo 也包含这些二进制项所依赖的库。其他项目也能用 Cargo 库来实现与 Cargo 命令行程序一样的逻辑。</p>
<p>包中可以包含至多一个库 crate(library crate)。包中可以包含任意多个二进制 crate(binary crate),但是必须至少包含一个 crate无论是库的还是二进制的</p>
<p>让我们来看看创建包的时候会发生什么。首先,我们输入命令 <code>cargo new</code></p>
<pre><code class="language-console">$ cargo new my-project
Created binary (application) `my-project` package
$ ls my-project
Cargo.toml
src
$ ls my-project/src
main.rs
</code></pre>
<p>运行了这条命令后,我们先用 <code>ls</code> (译者注:此命令为 Linux 平台的指令Windows 下可用 dir来看看 Cargo 给我们创建了什么Cargo 会给我们的包创建一个 <em>Cargo.toml</em> 文件。查看 <em>Cargo.toml</em> 的内容,会发现并没有提到 <em>src/main.rs</em>,因为 Cargo 遵循的一个约定:<em>src/main.rs</em> 就是一个与包同名的二进制 crate 的 crate 根。同样的Cargo 知道如果包目录中包含 <em>src/lib.rs</em>,则包带有与其同名的库 crate<em>src/lib.rs</em> 是 crate 根。crate 根文件将由 Cargo 传递给 <code>rustc</code> 来实际构建库或者二进制项目。</p>
<p>在此,我们有了一个只包含 <em>src/main.rs</em> 的包,意味着它只含有一个名为 <code>my-project</code> 的二进制 crate。如果一个包同时含有 <em>src/main.rs</em><em>src/lib.rs</em>,则它有两个 crate一个二进制的和一个库的且名字都与包相同。通过将文件放在 <em>src/bin</em> 目录下,一个包可以拥有多个二进制 crate每个 <em>src/bin</em> 下的文件都会被编译成一个独立的二进制 crate。</p>
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