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<ul class="chapter"><li><a href="ch01-00-introduction.html"><strong>1.</strong> 介绍</a></li><li><ul class="section"><li><a href="ch01-01-installation.html"><strong>1.1.</strong> 安装</a></li><li><a href="ch01-02-hello-world.html"><strong>1.2.</strong> Hello, World!</a></li></ul></li><li><a href="ch02-00-guessing-game-tutorial.html"><strong>2.</strong> 猜猜看教程</a></li><li><a href="ch03-00-common-programming-concepts.html"><strong>3.</strong> 通用编程概念</a></li><li><ul class="section"><li><a href="ch03-01-variables-and-mutability.html"><strong>3.1.</strong> 变量和可变性</a></li><li><a href="ch03-02-data-types.html"><strong>3.2.</strong> 数据类型</a></li><li><a href="ch03-03-how-functions-work.html"><strong>3.3.</strong> 函数如何工作</a></li><li><a href="ch03-04-comments.html"><strong>3.4.</strong> 注释</a></li><li><a href="ch03-05-control-flow.html"><strong>3.5.</strong> 控制流</a></li></ul></li><li><a href="ch04-00-understanding-ownership.html"><strong>4.</strong> 认识所有权</a></li><li><ul class="section"><li><a 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<code>panic!</code>还是不<code>panic!</code></a></li></ul></li><li><a href="ch10-00-generics.html"><strong>10.</strong> 泛型、trait 和生命周期</a></li><li><ul class="section"><li><a href="ch10-01-syntax.html"><strong>10.1.</strong> 泛型数据类型</a></li><li><a href="ch10-02-traits.html"><strong>10.2.</strong> trait定义共享的行为</a></li><li><a href="ch10-03-lifetime-syntax.html"><strong>10.3.</strong> 生命周期与引用有效性</a></li></ul></li><li><a href="ch11-00-testing.html"><strong>11.</strong> 测试</a></li><li><ul class="section"><li><a href="ch11-01-writing-tests.html"><strong>11.1.</strong> 编写测试</a></li><li><a href="ch11-02-running-tests.html"><strong>11.2.</strong> 运行测试</a></li><li><a href="ch11-03-test-organization.html"><strong>11.3.</strong> 测试的组织结构</a></li></ul></li><li><a href="ch12-00-an-io-project.html"><strong>12.</strong> 一个 I/O 项目</a></li><li><ul class="section"><li><a href="ch12-01-accepting-command-line-arguments.html"><strong>12.1.</strong> 接受命令行参数</a></li><li><a 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运行清理代码</a></li><li><a href="ch15-04-rc.html"><strong>15.4.</strong> <code>Rc&lt;T&gt;</code> 引用计数智能指针</a></li><li><a href="ch15-05-interior-mutability.html"><strong>15.5.</strong> <code>RefCell&lt;T&gt;</code>和内部可变性模式</a></li><li><a href="ch15-06-reference-cycles.html"><strong>15.6.</strong> 引用循环和内存泄漏是安全的</a></li></ul></li></ul>
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<a class="header" href="#cargo-工作空间" name="cargo-工作空间"><h2>Cargo 工作空间</h2></a>
<blockquote>
<p><a href="https://github.com/rust-lang/book/blob/master/second-edition/src/ch14-03-cargo-workspaces.md">ch14-03-cargo-workspaces.md</a>
<br>
commit d945f6d4046f4fc3c09326213100492790aebb45</p>
</blockquote>
<p>第十二章中,我们构建一个包含二进制 crate 和库 crate 的包。不过如果库 crate 继续变得更大而我们想要进一步将包拆分为多个库 crate 呢随着包增长拆分出其主要组件将是非常有帮助的。对于这种情况Cargo 提供了一个叫<strong>工作空间</strong><em>workspaces</em>)的功能,它可以帮助我们管理多个相关的并行开发的包。</p>
<p><strong>工作空间</strong>是一系列的包都共享同样的 <em>Cargo.lock</em> 和输出目录。让我们使用工作空间创建一个项目,这是我们熟悉的所以就可以关注工作空间的结构了。这里有一个二进制项目它使用了两个库:一个会提供<code>add_one</code>方法而第二个会提供<code>add_two</code>方法。让我们为这个二进制项目创建一个新 crate 作为开始:</p>
<pre><code>$ cargo new --bin adder
Created binary (application) `adder` project
$ cd adder
</code></pre>
<p>需要修改二进制包的 <em>Cargo.toml</em> 来告诉 Cargo 包<code>adder</code>是一个工作空间。再文件末尾增加如下:</p>
<pre><code class="language-toml">[workspace]
</code></pre>
<p>类似于很多 Cargo 的功能,工作空间支持配置惯例:只要遵循这些惯例就无需再增加任何配置了。这个惯例是任何作为子目录依赖的 crate 将是工作空间的一部分。让我们像这样在 <em>Cargo.toml</em> 中的<code>[dependencies]</code>增加一个<code>adder</code> crate 的路径依赖:</p>
<pre><code class="language-toml">[dependencies]
add-one = { path = &quot;add-one&quot; }
</code></pre>
<p>如果增加依赖但没有指定<code>path</code>,这将是一个不位于工作空间的正常的依赖。</p>
<p>接下来,在<code>adder</code>目录中生成<code>add-one</code> crate</p>
<pre><code>$ cargo new add-one
Created library `add-one` project
</code></pre>
<p>现在<code>adder</code>目录应该有如下目录和文件:</p>
<pre><code>├── Cargo.toml
├── add-one
│ ├── Cargo.toml
│ └── src
│ └── lib.rs
└── src
└── main.rs
</code></pre>
<p><em>add-one/src/lib.rs</em> 中增加<code>add_one</code>函数的实现:</p>
<p><span class="filename">Filename: add-one/src/lib.rs</span></p>
<pre><code class="language-rust">pub fn add_one(x: i32) -&gt; i32 {
x + 1
}
</code></pre>
<p>打开<code>adder</code><em>src/main.rs</em> 并增加一行<code>extern crate</code>将新的<code>add-one</code>库引入作用域,并修改<code>main</code>函数来使用<code>add_one</code>函数:</p>
<pre><code class="language-rust,ignore">extern crate add_one;
fn main() {
let num = 10;
println!(&quot;Hello, world! {} plus one is {}!&quot;, num, add_one::add_one(num));
}
</code></pre>
<p>让我们构建一下!</p>
<pre><code>$ cargo build
Compiling add-one v0.1.0 (file:///projects/adder/add-one)
Compiling adder v0.1.0 (file:///projects/adder)
Finished debug [unoptimized + debuginfo] target(s) in 0.68 secs
</code></pre>
<p>注意在 <em>adder</em> 目录运行<code>cargo build</code>会构建这个 crate 和 <em>adder/add-one</em> 中的<code>add-one</code> crate不过只创建一个 <em>Cargo.lock</em> 和一个 <em>target</em> 目录,他们都位于 <em>adder</em> 目录。试试你能否用相同的方式增加<code>add-two</code> crate。</p>
<p>假如我们想要在<code>add-one</code> crate 中使用<code>rand</code> crate。一如既往在<code>Cargo.toml</code><code>[dependencies]</code>部分增加这个 crate</p>
<p><span class="filename">Filename: add-one/Cargo.toml</span></p>
<pre><code class="language-toml">[dependencies]
rand = &quot;0.3.14&quot;
</code></pre>
<p>如果在 <em>add-one/src/lib.rs</em> 中加上<code>extern crate rand;</code>后再运行<code>cargo build</code>,则会编译成功:</p>
<pre><code>$ cargo build
Updating registry `https://github.com/rust-lang/crates.io-index`
Downloading rand v0.3.14
...snip...
Compiling rand v0.3.14
Compiling add-one v0.1.0 (file:///projects/adder/add-one)
Compiling adder v0.1.0 (file:///projects/adder)
Finished debug [unoptimized + debuginfo] target(s) in 10.18 secs
</code></pre>
<p>现在 <em>Cargo.lock</em> 的顶部反映了<code>add-one</code>依赖<code>rand</code>这一事实。然而即使在工作空间的某处使用了<code>rand</code>,也不能在工作空间的其他 crate 使用它,除非在对应的 <em>Cargo.toml</em> 也增加<code>rand</code>的依赖。例如,如果在顶层的<code>adder</code> crate 的 <em>src/main.rs</em> 中增加<code>extern crate rand;</code>,将会出现一个错误:</p>
<pre><code>$ cargo build
Compiling adder v0.1.0 (file:///projects/adder)
error[E0463]: can't find crate for `rand`
--&gt; src/main.rs:1:1
|
1 | extern crate rand;
| ^^^^^^^^^^^^^^^^^^^ can't find crate
</code></pre>
<p>为了修复这个错误,修改顶层的 <em>Cargo.toml</em> 并表明<code>rand</code><code>adder</code> crate 的一个依赖。</p>
<p>作为另一个提高,为 crate 中的<code>add_one::add_one</code>函数增加一个测试:</p>
<p><span class="filename">Filename: add-one/src/lib.rs</span></p>
<pre><code class="language-rust">pub fn add_one(x: i32) -&gt; i32 {
x + 1
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn it_works() {
assert_eq!(3, add_one(2));
}
}
</code></pre>
<p>现在在顶层的 <em>adder</em> 目录运行<code>cargo test</code></p>
<pre><code>$ cargo test
Compiling adder v0.1.0 (file:///projects/adder)
Finished debug [unoptimized + debuginfo] target(s) in 0.27 secs
Running target/debug/adder-f0253159197f7841
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured
</code></pre>
<p>等等,零个测试?我们不是刚增加了一个吗?如果我们观察输出,就不难发现在工作空间中的<code>cargo test</code>只运行顶层 crate 的测试。为了运行其他 crate 的测试,需要使用<code>-p</code>参数来表明我们希望与逆行测试包的测试:</p>
<pre><code>$ cargo test -p add-one
Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
Running target/debug/deps/add_one-abcabcabc
running 1 test
test tests::it_works ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured
Doc-tests add-one
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured
</code></pre>
<p>类似的,如果选择将工作空间发布到 crates.io其中的每一个包都需要单独发布。</p>
<p>随着项目增长,考虑使用工作空间:每一个更小的组件比一大块代码要容易理解。将 crate 保持在工作空间中易于协调他们的改变,如果他们一起运行并经常需要同时被修改的话。</p>
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