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<!DOCTYPE html>
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<title>Ruby on Rails 教程 - 第 6 章 用户模型</title>
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<article class="article">
<section data-type="chapter" id="modeling-users">
<h1><span class="title-label">第 6 章</span> 用户模型</h1>
<p><a href="chapter5.html#filling-in-the-layout">第 5 章</a>末尾创建了一个临时的用户注册页面（<a href="chapter5.html#user-signup-a-first-step">5.4 节</a>）。本书接下来的五章会逐步在这个页面中添加功能。本章我们要迈出关键的一步，创建网站中用户的数据模型，并实现存储数据的方式。<a href="chapter7.html#sign-up">第 7 章</a>会实现用户注册功能，并创建用户资料页面。用户能注册后，我们要实现登录和退出功能（<a href="chapter8.html#log-in-log-out">第 8 章</a>）。<a href="chapter9.html#updating-showing-and-deleting-users">第 9 章</a>（<a href="chapter9.html#requiring-logged-in-users">9.2.1 节</a>）会介绍如何保护页面，禁止无权限的用户访问。最后，在<a href="chapter10.html#account-activation-and-password-reset">第 10 章</a>实现账户激活（从而确认电子邮件地址有效）和密码重设功能。第 6 章到第 10 章的内容结合在一起，为 Rails 应用开发一个功能完整的登录和认证系统。或许你知道已经有很多开发好的 Rails 认证方案，<a href="#aside-roll-your-own">旁注 6.1</a>解释了为什么，至少在初学阶段，最好自己动手实现。</p>
<div data-type="sidebar" id="aside-roll-your-own" class="sidebar">
<h5><span class="title-label">旁注 6.1</span>：自己开发认证系统</h5>
<p>基本上所有 Web 应用都需要某种登录和认证系统。为此，大多数 Web 框架都提供了多种实现方式，Rails 也不例外。为 Rails 开发的认证和权限系统有 <a href="http://github.com/thoughtbot/clearance">Clearance</a>、<a href="http://github.com/binarylogic/authlogic">Authlogic</a>、<a href="http://github.com/plataformatec/devise">Devise</a> 和 <a href="http://railscasts.com/episodes/192-authorization-with-cancan">CanCan</a>。除此之外，还有一些不是 Rails 专用的方案，基于 <a href="http://en.wikipedia.org/wiki/OpenID">OpenID</a> 和 <a href="http://en.wikipedia.org/wiki/Oauth">OAuth</a> 实现。所以你肯定会问，为什么我们要重复制造轮子，为什么不直接使用现成的方案，而要自己开发呢？</p>
<p>首先，实践已经证明，大多数网站的认证系统都要对第三方代码库做一些定制和修改，这往往比重新开发一个工作量还大。再者，现成的方案就像一个“黑盒”，你无法了解其中到底有些什么功能，而自己开发的话能更好地理解实现的过程。而且，Rails 最近的更新（参见 <a href="#adding-a-secure-password">6.3 节</a>），让开发认证系统变得很简单。最后，如果以后要用第三方系统的话，因为自己开发过，所以能更好地理解实现过程，便于定制功能。</p>
</div>
<section data-type="sect1" id="user-model">
<h1><span class="title-label">6.1</span> 用户模型</h1>
<p>接下来的三章要实现网站的“注册”页面（构思图如<a href="#fig-signup-mockup-preview">图 6.1</a> 所示），在此之前我们先要解决存储问题，因为现在还没地方存储用户信息。所以，实现用户注册功能的第一步是，创建一个数据结构，获取并存储用户的信息。</p>
<div id="fig-signup-mockup-preview" class="figure"><img src="images/chapter6/signup_mockup_bootstrap.png" alt="signup mockup bootstrap" /><div class="figcaption"><span class="title-label">图 6.1</span>：用户注册页面的构思图</div></div>
<p>在 Rails 中，数据模型的默认数据结构叫“模型”（model，MVC 中的 M，参见 <a href="chapter1.html#model-view-controller">1.3.3 节</a>）。Rails 为解决数据持久化提供的默认解决方案是，使用数据库存储需要长期使用的数据。和数据库交互默认使用的是 Active Record。<sup>[<a id="fn-ref-1" href="#fn-1">1</a>]</sup>Active Record 提供了一系列方法，无需使用<a href="http://en.wikipedia.org/wiki/Relational_database">关系数据库</a>所用的“结构化查询语言”（Structured Query Language，简称 SQL），<sup>[<a id="fn-ref-2" href="#fn-2">2</a>]</sup>就能创建、保存和查询数据对象。Rails 还支持“迁移”（migration）功能，允许我们使用纯 Ruby 代码定义数据结构，而不用学习 SQL “数据定义语言”（Data Definition Language，简称 DDL）。最终的结果是，Active Record 把你和数据存储层完全隔开了。本书开发的应用在本地使用 SQLite，部署后使用 PostgreSQL（由 Heroku 提供，参见 <a href="chapter1.html#deploying">1.5 节</a>）。这就引出了一个更深层的话题——在不同的环境中，即便使用不同类型的数据库，我们也无需关心 Rails 是如何存储数据的。</p>
<p>和之前一样，如果使用 Git 做版本控制，现在应该新建一个主题分支：</p>
<div data-type="listing">
<div class="highlight language-sh"><pre><span class="nv">$ </span>git checkout master
<span class="nv">$ </span>git checkout -b modeling-users
</pre></div>
</div>
<section data-type="sect2" id="database-migrations">
<h2><span class="title-label">6.1.1</span> 数据库迁移</h2>
<p>回顾一下 <a href="chapter4.html#a-user-class">4.4.5 节</a>的内容，在我们自己创建的 <code>User</code> 类中为用户对象定义了 <code>name</code> 和 <code>email</code> 两个属性。那是个很有用的例子，但没有实现持久性最关键的要求：在 Rails 控制台中创建的用户对象，退出控制台后就会消失。本节的目的是为用户创建一个模型，让用户数据不会这么轻易消失。</p>
<p>和 <a href="chapter4.html#a-user-class">4.4.5 节</a>中定义的 <code>User</code> 类一样，我们先为用户模型创建两个属性，分别是 <code>name</code> 和 <code>email</code>。我们会把 <code>email</code> 属性用作唯一的用户名。<sup>[<a id="fn-ref-3" href="#fn-3">3</a>]</sup>（<a href="#adding-a-secure-password">6.3 节</a>会添加一个属性，存储密码）在<a href="chapter4.html#listing-example-user">代码清单 4.13</a> 中，我们使用 Ruby 的 <code>attr_accessor</code> 方法创建了这两个属性：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">User</span>
<span class="kp">attr_accessor</span> <span class="ss">:name</span><span class="p">,</span> <span class="ss">:email</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="k">end</span>
</pre></div>
</div>
<p>不过，在 Rails 中不用这样定义属性。前面提到过，Rails 默认使用关系数据库存储数据，数据库中的表由数据行组成，每一行都有相应的列，对应数据属性。例如，为了存储用户的名字和电子邮件地址，我们要创建 <code>users</code> 表，表中有两个列，<code>name</code> 和 <code>email</code>，这样每一行就表示一个用户，如<a href="#fig-users-table">图 6.2</a> 所示，对应的数据模型如<a href="#fig-user-model-sketch">图 6.3</a> 所示。（图 6.3 只是梗概，完整的数据模型如<a href="#fig-user-model-initial">图 6.4</a> 所示。）把列命名为 <code>name</code> 和 <code>email</code> 后，Active Record 会自动把它们识别为用户对象的属性。</p>
<div id="fig-users-table" class="figure"><img src="images/chapter6/users_table.png" alt="users table" /><div class="figcaption"><span class="title-label">图 6.2</span>：<code>users</code> 表中的示例数据</div></div>
<div id="fig-user-model-sketch" class="figure"><img src="images/chapter6/user_model_sketch.png" alt="user model sketch" /><div class="figcaption"><span class="title-label">图 6.3</span>：用户数据模型梗概</div></div>
<p>你可能还记得，在<a href="chapter5.html#listing-generate-users-controller">代码清单 5.28</a> 中，我们使用下面的命令生成了用户控制器和 <code>new</code> 动作：</p>
<div data-type="listing">
<div class="highlight language-sh"><pre><span class="nv">$ </span>rails generate controller Users new
</pre></div>
</div>
<p>创建模型有个类似的命令——<code>generate model</code>。我们可以使用这个命令生成用户模型，以及 <code>name</code> 和 <code>email</code> 属性，如<a href="#listing-generate-user-model">代码清单 6.1</a> 所示。</p>
<div id="listing-generate-user-model" data-type="listing">
<h5><span class="title-label">代码清单 6.1</span>：生成用户模型</h5>
<div class="highlight language-sh"><pre><span class="nv">$ </span>rails generate model User name:string email:string
invoke active_record
create db/migrate/20140724010738_create_users.rb
create app/models/user.rb
invoke test_unit
create <span class="nb">test</span>/models/user_test.rb
create <span class="nb">test</span>/fixtures/users.yml
</pre></div>
</div>
<p>（注意，控制器名是复数，模型名是单数：控制器是 <code>Users</code>，而模型是 <code>User</code>。）我们指定了可选的参数 <code>name:string</code> 和 <code>email:string</code>，告诉 Rails 我们需要的两个属性是什么，以及各自的类型（两个都是字符串）。你可以把这两个参数与<a href="chapter3.html#listing-generating-pages">代码清单 3.4</a> 和<a href="chapter5.html#listing-generate-users-controller">代码清单 5.28</a> 中的动作名对比一下，看看有什么不同。</p>
<p>执行上述 <code>generate</code> 命令之后，会生成一个迁移文件。迁移是一种递进修改数据库结构的方式，可以根据需求修改数据模型。执行 <code>generate</code> 命令后会自动为用户模型创建迁移，这个迁移的作用是创建一个 <code>users</code> 表以及 <code>name</code> 和 <code>email</code> 两个列，如<a href="#listing-users-migration">代码清单 6.2</a> 所示。（我们会在 <a href="#uniqueness-validation">6.2.5 节</a>介绍如何手动创建迁移文件。）</p>
<div id="listing-users-migration" data-type="listing">
<h5><span class="title-label">代码清单 6.2</span>：用户模型的迁移文件（创建 <code>users</code> 表）</h5>
<div class="source-file">db/migrate/[timestamp]_create_users.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">CreateUsers</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Migration</span>
<span class="k">def</span> <span class="nf">change</span>
<span class="n">create_table</span> <span class="ss">:users</span> <span class="k">do</span> <span class="o">|</span><span class="n">t</span><span class="o">|</span>
<span class="n">t</span><span class="o">.</span><span class="n">string</span> <span class="ss">:name</span>
<span class="n">t</span><span class="o">.</span><span class="n">string</span> <span class="ss">:email</span>
<span class="n">t</span><span class="o">.</span><span class="n">timestamps</span> <span class="ss">null</span><span class="p">:</span> <span class="kp">false</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">end</span>
</pre></div>
</div>
<p>注意，迁移文件名前面有个时间戳，指明创建的时间。早期，迁移文件名的前缀是递增的数字，在团队协作中，如果多个程序员生成了序号相同的迁移文件就可能会发生冲突。除非两个迁移文件在同一秒钟生成这种小概率事件发生了，否则使用时间戳基本可以避免冲突的发生。</p>
<p>迁移文件中有一个名为 <code>change</code> 的方法，定义要对数据库做什么操作。在<a href="#listing-users-migration">代码清单 6.2</a> 中，<code>change</code> 方法使用 Rails 提供的 <code>create_table</code> 方法在数据库中新建一个表，用来存储用户。<code>create_table</code> 方法可以接受一个块，块中有一个块变量 <code>t</code>（“table”）。在块中，<code>create_table</code> 方法通过 <code>t</code> 对象创建 <code>name</code> 和 <code>email</code> 两个列，均为 <code>string</code> 类型。<sup>[<a id="fn-ref-4" href="#fn-4">4</a>]</sup>表名是复数形式（<code>users</code>），不过模型名是单数形式（<code>User</code>），这是 Rails 在用词上的一个约定：模型表示单个用户，而数据库表中存储了很多用户。块中最后一行 <code>t.timestamps null: false</code> 是个特殊的方法，它会自动创建两个列，<code>created_at</code> 和 <code>updated_at</code>，这两个列分别记录创建用户的时间戳和更新用户数据的时间戳。（<a href="#creating-user-objects">6.1.3 节</a>有使用这两个列的例子。）这个迁移文件表示的完整数据模型如<a href="#fig-user-model-initial">图 6.4</a> 所示。（注意，<a href="#fig-user-model-sketch">图 6.3</a> 中没有列出自动添加的两个时间戳列。）</p>
<div id="fig-user-model-initial" class="figure"><img src="images/chapter6/user_model_initial_3rd_edition.png" alt="user model initial 3rd edition" /><div class="figcaption"><span class="title-label">图 6.4</span>：<a href="#listing-users-migration">代码清单 6.2</a> 生成的用户数据模型</div></div>
<p>我们可以使用如下的 <code>rake</code> 命令（<a href="chapter2.html#aside-rake">旁注 2.1</a>）执行这个迁移（叫“向上迁移”）：</p>
<div data-type="listing">
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake db:migrate
</pre></div>
</div>
<p>（你可能还记得，我们在 <a href="chapter2.html#the-users-resource">2.2 节</a>用过这个命令。）第一次运行 <code>db:migrate</code> 命令时会创建 <code>db/development.sqlite3</code>，这是 SQLite <sup>[<a id="fn-ref-5" href="#fn-5">5</a>]</sup>数据库文件。若要查看数据库结构，可以使用 <a href="http://sqlitebrowser.org/">SQLite 数据库浏览器</a>打开 <code>db/development.sqlite3</code> 文件，如<a href="#fig-sqlite-database-browser">图 6.5</a> 所示。（如果想从云端 IDE 把这个文件下载到本地电脑，可以在 <code>db/development.sqlite3</code> 上按右键，然后选择“Download”。）和<a href="#fig-user-model-initial">图 6.4</a> 中的模型对比之后，你可能会发现有一个列在迁移中没有出现——<code>id</code> 列。<a href="chapter2.html#the-users-resource">2.2 节</a>提到过，这个列是自动生成的，Rails 用这个列作为行的唯一标识符。</p>
<div id="fig-sqlite-database-browser" class="figure"><img src="images/chapter6/sqlite_database_browser_3rd_edition.png" alt="sqlite database browser 3rd edition" /><div class="figcaption"><span class="title-label">图 6.5</span>：在 SQLite 数据库浏览器中查看刚创建的 <code>users</code> 表</div></div>
<p>大多数迁移，包括本书中的所有迁移，都是可逆的，也就是说可以使用一个简单的 Rake 命令“向下迁移”，撤销之前的操作，这个命令是 <code>db:rollback</code>：</p>
<div data-type="listing">
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake db:rollback
</pre></div>
</div>
<p>（还有一个撤销迁移的方法，参见<a href="chapter3.html#aside-undoing-things">旁注 3.1</a>。）这个命令会调用 <code>drop_table</code> 方法，把 <code>users</code> 表从数据库中删除。之所以可以这么做，是因为 <code>change</code> 方法知道 <code>create_table</code> 的逆操作是 <code>drop_table</code>，所以回滚时会直接调用 <code>drop_table</code> 方法。对于一些无法自动逆转的操作，例如删除列，就不能依赖 <code>change</code> 方法了，我们要分别定义 <code>up</code> 和 <code>down</code> 方法。关于迁移的更多信息请查看 <a href="http://guides.rubyonrails.org/migrations.html">Rails 指南</a>。</p>
<p>如果你执行了上面的回滚操作，在继续阅读之前请再迁移回来：</p>
<div data-type="listing">
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake db:migrate
</pre></div>
</div>
</section>
<section data-type="sect2" id="the-model-file">
<h2><span class="title-label">6.1.2</span> 模型文件</h2>
<p>我们看到，执行<a href="#listing-generate-user-model">代码清单 6.1</a> 中的命令后会生成一个迁移文件（<a href="#listing-users-migration">代码清单 6.2</a>），也看到了执行迁移后得到的结果（<a href="#fig-sqlite-database-browser">图 6.5</a>）：修改 <code>db/development.sqlite3</code> 文件，新建 <code>users</code> 表，并创建 <code>id</code>、<code>name</code>、<code>email</code>、<code>created_at</code> 和 <code>updated_at</code> 这几个列。<a href="#listing-generate-user-model">代码清单 6.1</a> 同时还生成了一个模型文件，本节剩下的内容专门解说这个文件。</p>
<p>我们先看用户模型的代码，在 <code>app/models/</code> 文件夹中的 <code>user.rb</code> 文件里。这个文件的内容非常简单，如<a href="#listing-raw-user-model">代码清单 6.3</a> 所示。</p>
<div id="listing-raw-user-model" data-type="listing">
<h5><span class="title-label">代码清单 6.3</span>：刚创建的用户模型</h5>
<div class="source-file">app/models/user.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">User</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Base</span>
<span class="k">end</span>
</pre></div>
</div>
<p><a href="chapter4.html#class-inheritance">4.4.2 节</a>介绍过，<code>class User < ActiveRecord::Base</code> 的意思是 <code>User</code> 类继承自 <code>ActiveRecord::Base</code> 类，所以用户模型自动获得了 <code>ActiveRecord::Base</code> 的所有功能。当然了，只知道这种继承关系没什么用，我们并不知道 <code>ActiveRecord::Base</code> 做了什么。下面看几个实例。</p>
</section>
<section data-type="sect2" id="creating-user-objects">
<h2><span class="title-label">6.1.3</span> 创建用户对象</h2>
<p>和<a href="chapter4.html#rails-flavored-ruby">第 4 章</a>一样，探索数据模型使用的工具是 Rails 控制台。因为我们还不想修改数据库中的数据，所以要在沙盒模式中启动控制台：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="go">$ rails console --sandbox</span>
<span class="go">Loading development environment in sandbox</span>
<span class="go">Any modifications you make will be rolled back on exit</span>
<span class="go">>></span>
</pre></div>
</div>
<p>如提示消息所说，“Any modifications you make will be rolled back on exit”，在沙盒模式下使用控制台，退出当前会话后，对数据库做的所有改动都会回归到原来的状态。</p>
<p>在 <a href="chapter4.html#a-user-class">4.4.5 节</a>的控制台会话中，我们要引入<a href="chapter4.html#listing-example-user">代码清单 4.13</a> 中的代码才能使用 <code>User.new</code> 创建用户对象。对模型来说，情况有所不同。你可能还记得 <a href="chapter4.html#a-controller-class">4.4.4 节</a>说过，Rails 控制台会自动加载 Rails 环境，这其中就包括模型。也就是说，现在无需加载任何代码就可以直接创建用户对象：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="no">User</span><span class="o">.</span><span class="n">new</span>
<span class="go">=> #<User id: nil, name: nil, email: nil, created_at: nil, updated_at: nil></span>
</pre></div>
</div>
<p>上述代码显示了一个用户对象的默认值。</p>
<p>如果不为 <code>User.new</code> 指定参数，对象的所有属性值都是 <code>nil</code>。在 <a href="chapter4.html#a-user-class">4.4.5 节</a>，自己编写的 <code>User</code> 类可以接受一个哈希参数初始化对象的属性。这种方式是受 Active Record 启发的，在 Active Record 中也可以使用相同的方式指定初始值：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"Michael Hartl"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="go">=> #<User id: nil, name: "Michael Hartl", email: "[email protected]", created_at: nil, updated_at: nil></span>
</pre></div>
</div>
<p>我们看到 <code>name</code> 和 <code>email</code> 属性的值都已经设定了。</p>
<p>数据的有效性对理解 Active Record 模型对象很重要，我们会在 <a href="#user-validations">6.2 节</a>深入介绍。不过注意，现在这个 <code>user</code> 对象是有效的，我们可以在这个对象上调用 <code>valid?</code> 方法确认：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">valid?</span>
<span class="go">true</span>
</pre></div>
</div>
<p>到目前为止，我们都没有修改数据库：<code>User.new</code> 只在内存中创建一个对象，<code>user.valid?</code> 只是检查对象是否有效。如果想把用户对象保存到数据库中，我们要在 <code>user</code> 变量上调用 <code>save</code> 方法：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">save</span>
<span class="go"> (0.2ms) begin transaction</span>
<span class="go"> User Exists (0.2ms) SELECT 1 AS one FROM "users" WHERE LOWER("users".</span>
<span class="go"> "email") = LOWER('[email protected]') LIMIT 1</span>
<span class="go"> SQL (0.5ms) INSERT INTO "users" ("created_at", "email", "name", "updated_at)</span>
<span class="go"> VALUES (?, ?, ?, ?) [["created_at", "2014-09-11 14:32:14.199519"],</span>
<span class="go"> ["email", "[email protected]"], ["name", "Michael Hartl"], ["updated_at",</span>
<span class="go"> "2014-09-11 14:32:14.199519"]]</span>
<span class="go"> (0.9ms) commit transaction</span>
<span class="go">=> true</span>
</pre></div>
</div>
<p>如果保存成功，<code>save</code> 方法返回 <code>true</code>，否则返回 <code>false</code>。（现在所有保存操作都会成功，因为还没有数据验证功能，<a href="#user-validations">6.2 节</a>会看到一些失败的例子。）Rails 还会在控制台中显示 <code>user.save</code> 对应的 SQL 语句（<code>INSERT INTO "users"…</code>），以供参考。本书几乎不会使用原始的 SQL，<sup>[<a id="fn-ref-6" href="#fn-6">6</a>]</sup>所以此后会省略 SQL。不过，从 Active Record 各种操作生成的 SQL 中可以学到很多知识。</p>
<p>你可能注意到了，刚创建时用户对象的 <code>id</code>、<code>created_at</code> 和 <code>updated_at</code> 属性值都是 <code>nil</code>，下面看一下保存之后有没有变化：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span>
<span class="go">=> #<User id: 1, name: "Michael Hartl", email: "[email protected]",</span>
<span class="go">created_at: "2014-07-24 00:57:46", updated_at: "2014-07-24 00:57:46"></span>
</pre></div>
</div>
<p>我们看到，<code>id</code> 的值变成了 <code>1</code>，那两个自动创建的时间戳属性也变成了当前时间。<sup>[<a id="fn-ref-7" href="#fn-7">7</a>]</sup>现在这两个时间戳是一样的，<a href="#updating-user-objects">6.1.5 节</a>会看到二者不同的情况。</p>
<p>和 <a href="chapter4.html#a-user-class">4.4.5 节</a>的 <code>User</code> 类一样，用户模型的实例也可以使用点号获取属性：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">name</span>
<span class="go">=> "Michael Hartl"</span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">email</span>
<span class="go">=> "[email protected]"</span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">updated_at</span>
<span class="go">=> Thu, 24 Jul 2014 00:57:46 UTC +00:00</span>
</pre></div>
</div>
<p><a href="chapter7.html#sign-up">第 7 章</a>会介绍，虽然一般习惯把创建和保存分成如上所示的两步完成，不过 Active Record 也允许我们使用 <code>User.create</code> 方法把这两步合成一步：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="no">User</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"A Nother"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="go">#<User id: 2, name: "A Nother", email: "[email protected]", created_at:</span>
<span class="go">"2014-07-24 01:05:24", updated_at: "2014-07-24 01:05:24"></span>
<span class="gp">>> </span><span class="n">foo</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"Foo"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="go">#<User id: 3, name: "Foo", email: "[email protected]", created_at: "2014-07-24</span>
<span class="go">01:05:42", updated_at: "2014-07-24 01:05:42"></span>
</pre></div>
</div>
<p>注意，<code>User.create</code> 的返回值不是 <code>true</code> 或 <code>false</code>，而是创建的用户对象，可直接赋值给变量（例如上面第二个命令中的 <code>foo</code> 变量）.</p>
<p><code>create</code> 的逆操作是 <code>destroy</code>：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">foo</span><span class="o">.</span><span class="n">destroy</span>
<span class="go">=> #<User id: 3, name: "Foo", email: "[email protected]", created_at: "2014-07-24</span>
<span class="go">01:05:42", updated_at: "2014-07-24 01:05:42"></span>
</pre></div>
</div>
<p>奇怪的是，<code>destroy</code> 和 <code>create</code> 一样，返回值是对象。我不觉得什么地方会用到 <code>destroy</code> 的返回值。更奇怪的是，销毁的对象还在内存中：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">foo</span>
<span class="go">=> #<User id: 3, name: "Foo", email: "[email protected]", created_at: "2014-07-24</span>
<span class="go">01:05:42", updated_at: "2014-07-24 01:05:42"></span>
</pre></div>
</div>
<p>那么我们怎么知道对象是否真被销毁了呢？对于已经保存而没有销毁的对象，怎样从数据库中读取呢？要回答这些问题，我们要先学习如何使用 Active Record 查找用户对象。</p>
</section>
<section data-type="sect2" id="finding-user-objects">
<h2><span class="title-label">6.1.4</span> 查找用户对象</h2>
<p>Active Record 提供了好几种查找对象的方法。下面我们使用这些方法查找创建的第一个用户，同时也验证一下第三个用户（<code>foo</code>）是否被销毁了。先看一下还存在的用户：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="no">User</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="go">=> #<User id: 1, name: "Michael Hartl", email: "[email protected]",</span>
<span class="go">created_at: "2014-07-24 00:57:46", updated_at: "2014-07-24 00:57:46"></span>
</pre></div>
</div>
<p>我们把用户的 ID 传给 <code>User.find</code> 方法，Active Record 会返回 ID 为 1 的用户对象。</p>
<p>下面来看一下 ID 为 3 的用户是否还在数据库中：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="no">User</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>
<span class="go">ActiveRecord::RecordNotFound: Couldn't find User with ID=3</span>
</pre></div>
</div>
<p>因为我们在 <a href="#creating-user-objects">6.1.3 节</a>销毁了第三个用户，所以 Active Record 无法在数据库中找到这个用户，抛出了一个异常，这说明在查找过程中出现了问题。因为 ID 不存在，所以 <code>find</code> 方法抛出 <code>ActiveRecord::RecordNotFound</code> 异常。<sup>[<a id="fn-ref-8" href="#fn-8">8</a>]</sup></p>
<p>除了这种查找方法之外，Active Record 还支持通过属性查找用户：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="no">User</span><span class="o">.</span><span class="n">find_by</span><span class="p">(</span><span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="go">=> #<User id: 1, name: "Michael Hartl", email: "[email protected]",</span>
<span class="go">created_at: "2014-07-24 00:57:46", updated_at: "2014-07-24 00:57:46"></span>
</pre></div>
</div>
<p>我们会使用电子邮件地址做用户名，所以在学习如何让用户登录网站时会用到这种 <code>find</code> 方法（<a href="chapter7.html#sign-up">第 7 章</a>）。你可能会担心如果用户数量过多，使用 <code>find_by</code> 的效率不高。事实的确如此，我们会在 <a href="#uniqueness-validation">6.2.5 节</a>说明这个问题，以及如何使用数据库索引解决。</p>
<p>最后，再介绍几个常用的查找方法。首先是 <code>first</code> 方法：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="no">User</span><span class="o">.</span><span class="n">first</span>
<span class="go">=> #<User id: 1, name: "Michael Hartl", email: "[email protected]",</span>
<span class="go">created_at: "2014-07-24 00:57:46", updated_at: "2014-07-24 00:57:46"></span>
</pre></div>
</div>
<p>很明显，<code>first</code> 会返回数据库中的第一个用户。还有 <code>all</code> 方法：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="no">User</span><span class="o">.</span><span class="n">all</span>
<span class="go">=> #<ActiveRecord::Relation [#<User id: 1, name: "Michael Hartl",</span>
<span class="go">email: "[email protected]", created_at: "2014-07-24 00:57:46",</span>
<span class="go">updated_at: "2014-07-24 00:57:46">, #<User id: 2, name: "A Nother",</span>
<span class="go">email: "[email protected]", created_at: "2014-07-24 01:05:24",</span>
<span class="go">updated_at: "2014-07-24 01:05:24">]></span>
</pre></div>
</div>
<p>从控制台的输出可以看出，<code>User.all</code> 方法返回一个 <code>ActiveRecord::Relation</code> 实例，其实这是一个数组（<a href="chapter4.html#arrays-and-ranges">4.3.1 节</a>），
包含数据库中的所有用户。</p>
</section>
<section data-type="sect2" id="updating-user-objects">
<h2><span class="title-label">6.1.5</span> 更新用户对象</h2>
<p>创建对象后，一般都会进行更新操作。更新有两种基本方式，其一，可以分别为各属性赋值，在 <a href="chapter4.html#a-user-class">4.4.5 节</a>就是这么做的：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span> <span class="c1"># 只是为了查看 user 对象的属性是什么</span>
<span class="go">=> #<User id: 1, name: "Michael Hartl", email: "[email protected]",</span>
<span class="go">created_at: "2014-07-24 00:57:46", updated_at: "2014-07-24 00:57:46"></span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">email</span> <span class="o">=</span> <span class="s2">"[email protected]"</span>
<span class="go">=> "[email protected]"</span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">save</span>
<span class="go">=> true</span>
</pre></div>
</div>
<p>注意，如果想把改动写入数据库，必须执行最后一个方法。我们可以执行 <code>reload</code> 命令来看一下没保存的话是什么情况。<code>reload</code> 命令会使用数据库中的数据重新加载对象：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">email</span>
<span class="go">=> "[email protected]"</span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">email</span> <span class="o">=</span> <span class="s2">"[email protected]"</span>
<span class="go">=> "[email protected]"</span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">reload</span><span class="o">.</span><span class="n">email</span>
<span class="go">=> "[email protected]"</span>
</pre></div>
</div>
<p>现在我们已经更新了用户数据，如在 <a href="#creating-user-objects">6.1.3 节</a>中所说，自动创建的那两个时间戳属性不一样了：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">created_at</span>
<span class="go">=> "2014-07-24 00:57:46"</span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">updated_at</span>
<span class="go">=> "2014-07-24 01:37:32"</span>
</pre></div>
</div>
<p>更新数据的第二种常用方式是使用 <code>update_attributes</code> 方法：<sup>[<a id="fn-ref-9" href="#fn-9">9</a>]</sup></p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">update_attributes</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"The Dude"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="go">=> true</span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">name</span>
<span class="go">=> "The Dude"</span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">email</span>
<span class="go">=> "[email protected]"</span>
</pre></div>
</div>
<p><code>update_attributes</code> 方法接受一个指定对象属性的哈希作为参数，如果操作成功，会执行更新和保存两个操作（保存成功时返回值为 <code>true</code>）。注意，如果任何一个数据验证失败了，例如存储记录时需要密码（<a href="#adding-a-secure-password">6.3 节</a>实现），<code>update_attributes</code> 操作就会失败。如果只需要更新单个属性，可以使用 <code>update_attribute</code>，跳过验证：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">update_attribute</span><span class="p">(</span><span class="ss">:name</span><span class="p">,</span> <span class="s2">"The Dude"</span><span class="p">)</span>
<span class="go">=> true</span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">name</span>
<span class="go">=> "The Dude"</span>
</pre></div>
</div>
</section>
</section>
<section data-type="sect1" id="user-validations">
<h1><span class="title-label">6.2</span> 用户数据验证</h1>
<p><a href="#user-model">6.1 节</a>创建的用户模型现在已经有了可以使用的 <code>name</code> 和 <code>email</code> 属性，不过功能还很简单：任何字符串（包括空字符串）都可以使用。名字和电子邮件地址的格式显然要复杂一些。例如，<code>name</code> 不应该是空的，<code>email</code> 应该符合特定的格式。而且，我们要把电子邮件地址当成用户名用来登录，那么在数据库中就不能重复出现。</p>
<p>总之，<code>name</code> 和 <code>email</code> 不是什么字符串都可以使用的，我们要对它们可使用的值做个限制。Active Record 通过数据验证实现这种限制（<a href="chapter2.html#putting-the-micro-in-microposts">2.3.2 节</a>简单提到过）。本节，我们会介绍几种常用的数据验证：存在性、长度、格式和唯一性。<a href="#user-has-secure-password">6.3.2 节</a>还会介绍另一种常用的数据验证——二次确认。<a href="chapter7.html#unsuccessful-signups">7.3 节</a>会看到，如果提交了不合要求的数据，数据验证会显示一些很有用的错误消息。</p>
<section data-type="sect2" id="a-validity-test">
<h2><span class="title-label">6.2.1</span> 有效性测试</h2>
<p><a href="chapter3.html#aside-when-to-test">旁注 3.3</a>说过，TDD 并不适用所有情况，但是模型验证是使用 TDD 的绝佳时机。如果不先编写失败测试，再想办法让它通过，我们很难确定验证是否实现了我们希望实现的功能。</p>
<p>我们采用的方法是，先得到一个有效的模型对象，然后把属性改为无效值，以此确认这个对象是无效的。以防万一，我们先编写一个测试，确认模型对象一开始是有效的。这样，如果验证测试失败了，我们才知道的确事出有因（而不是因为一开始对象是无效的）。</p>
<p><a href="#listing-generate-user-model">代码清单 6.1</a> 中的命令生成了一个用来测试用户模型的测试文件，现在这个文件中还没什么内容，如<a href="#listing-default-user-test">代码清单 6.4</a> 所示。</p>
<div id="listing-default-user-test" data-type="listing">
<h5><span class="title-label">代码清单 6.4</span>：还没什么内容的用户模型测试文件</h5>
<div class="source-file">test/models/user_test.rb</div>
<div class="highlight language-ruby"><pre><span class="nb">require</span> <span class="s1">'test_helper'</span>
<span class="k">class</span> <span class="nc">UserTest</span> <span class="o"><</span> <span class="no">ActiveSupport</span><span class="o">::</span><span class="no">TestCase</span>
<span class="c1"># test "the truth" do</span>
<span class="c1"># assert true</span>
<span class="c1"># end</span>
<span class="k">end</span>
</pre></div>
</div>
<p>为了测试有效的对象，我们要在特殊的 <code>setup</code> 方法中创建一个有效的用户对象 <code>@user</code>。<a href="chapter3.html#mostly-static-pages-exercises">3.6 节</a>的练习中提到过，<code>setup</code> 方法会在每个测试方法运行前执行。因为 <code>@user</code> 是实例变量，所以自动可在所有测试方法中使用，而且我们可以使用 <code>valid?</code> 方法检查它是否有效。测试如<a href="#listing-valid-user-test">代码清单 6.5</a> 所示。</p>
<div id="listing-valid-user-test" data-type="listing">
<h5><span class="title-label">代码清单 6.5</span>：测试用户对象一开始是有效的 <span class="green">GREEN</span></h5>
<div class="source-file">test/models/user_test.rb</div>
<div class="highlight language-ruby"><pre><span class="nb">require</span> <span class="s1">'test_helper'</span>
<span class="k">class</span> <span class="nc">UserTest</span> <span class="o"><</span> <span class="no">ActiveSupport</span><span class="o">::</span><span class="no">TestCase</span>
<span class="k">def</span> <span class="nf">setup</span>
<span class="vi">@user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"Example User"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="k">end</span>
<span class="nb">test</span> <span class="s2">"should be valid"</span> <span class="k">do</span>
<span class="n">assert</span> <span class="vi">@user</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="k">end</span>
</pre></div>
</div>
<p><a href="#listing-valid-user-test">代码清单 6.5</a> 使用简单的 <code>assert</code> 方法，如果 <code>@user.valid?</code> 返回 <code>true</code>，测试就能通过；返回 <code>false</code>，测试则会失败。</p>
<p>因为用户模型现在还没有任何验证，所有这个测试可以通过：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 6.6</span>：<strong class="green">GREEN</strong></h5>
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake <span class="nb">test</span>:models
</pre></div>
</div>
<p>这里，我们使用 <code>rake test:models</code>，只运行模型测试（和 <a href="chapter5.html#layout-link-tests">5.3.4 节</a>的 <code>rake test:integration</code> 对比一下）。</p>
</section>
<section data-type="sect2" id="validating-presence">
<h2><span class="title-label">6.2.2</span> 存在性验证</h2>
<p>存在性验证算是最基本的验证了，只是检查指定的属性是否存在。本节我们会确保用户存入数据库之前，<code>name</code> 和 <code>email</code> 字段都有值。<a href="chapter7.html#signup-error-messages">7.3.3 节</a>会介绍如何把这个限制应用到创建用户的注册表单中。</p>
<p>我们要先在<a href="#listing-valid-user-test">代码清单 6.5</a> 的基础上再编写一个测试，检查 <code>name</code> 属性是否存在。如<a href="#listing-name-presence-test">代码清单 6.7</a> 所示，我们只需把 <code>@user</code> 的 <code>name</code> 属性设为空字符串（包含几个空格的字符串），然后使用 <code>assert_not</code> 方法确认得到的用户对象是无效的。</p>
<div id="listing-name-presence-test" data-type="listing">
<h5><span class="title-label">代码清单 6.7</span>：测试 <code>name</code> 属性的验证措施 <span class="red">RED</span></h5>
<div class="source-file">test/models/user_test.rb</div>
<div class="highlight language-ruby"><pre><span class="nb">require</span> <span class="s1">'test_helper'</span>
<span class="k">class</span> <span class="nc">UserTest</span> <span class="o"><</span> <span class="no">ActiveSupport</span><span class="o">::</span><span class="no">TestCase</span>
<span class="k">def</span> <span class="nf">setup</span>
<span class="vi">@user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"Example User"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="k">end</span>
<span class="nb">test</span> <span class="s2">"should be valid"</span> <span class="k">do</span>
<span class="n">assert</span> <span class="vi">@user</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="hll"> <span class="nb">test</span> <span class="s2">"name should be present"</span> <span class="k">do</span>
</span><span class="hll"> <span class="vi">@user</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="s2">" "</span>
</span><span class="hll"> <span class="n">assert_not</span> <span class="vi">@user</span><span class="o">.</span><span class="n">valid?</span>
</span><span class="hll"> <span class="k">end</span>
</span><span class="k">end</span>
</pre></div>
</div>
<p>现在，模型测试应该失败：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 6.8</span>：<strong class="red">RED</strong></h5>
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake <span class="nb">test</span>:models
</pre></div>
</div>
<p>我们在<a href="chapter2.html#a-toy-app-exercises">2.5 节</a>中见过，<code>name</code> 属性的存在性验证使用 <code>validates</code> 方法，而且其参数为 <code>presence: true</code>，如<a href="#listing-validates-presence-of-name">代码清单 6.9</a> 所示。<code>presence: true</code> 是只有一个元素的可选哈希参数，<a href="chapter4.html#css-revisited">4.3.4 节</a>说过，如果方法的最后一个参数是哈希，可以省略花括号。（<a href="chapter5.html#site-navigation">5.1.1 节</a>说过，Rails 经常使用哈希做参数。）</p>
<div id="listing-validates-presence-of-name" data-type="listing">
<h5><span class="title-label">代码清单 6.9</span>：添加 <code>name</code> 属性存在性验证 <span class="green">GREEN</span></h5>
<div class="source-file">app/models/user.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">User</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Base</span>
<span class="hll"> <span class="n">validates</span> <span class="ss">:name</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span>
</span><span class="k">end</span>
</pre></div>
</div>
<p><a href="#listing-validates-presence-of-name">代码清单 6.9</a> 中的代码看起来可能有点儿神奇，其实 <code>validates</code> 就是个方法。加入括号后，可以写成：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">User</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Base</span>
<span class="n">validates</span><span class="p">(</span><span class="ss">:name</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span><span class="p">)</span>
<span class="k">end</span>
</pre></div>
</div>
<p>打开控制台，看一下在用户模型中加入验证后有什么效果：<sup>[<a id="fn-ref-10" href="#fn-10">10</a>]</sup></p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="go">$ rails console --sandbox</span>
<span class="gp">>> </span><span class="n">user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">""</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">valid?</span>
<span class="go">=> false</span>
</pre></div>
</div>
<p>这里我们使用 <code>valid?</code> 方法检查 <code>user</code> 变量的有效性，如果有一个或多个验证失败，返回值为 <code>false</code>，如果所有验证都能通过，返回 <code>true</code>。现在只有一个验证，所以我们知道是哪一个失败，不过看一下失败时生成的 <code>errors</code> 对象还是很有用的：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">errors</span><span class="o">.</span><span class="n">full_messages</span>
<span class="go">=> ["Name can't be blank"]</span>
</pre></div>
</div>
<p>（错误消息暗示，Rails 使用 <a href="chapter4.html#modifying-built-in-classes">4.4.3 节</a>介绍的 <code>blank?</code> 方法验证存在性。）</p>
<p>因为用户无效，如果尝试把它保存到数据库中，操作会失败：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">save</span>
<span class="go">=> false</span>
</pre></div>
</div>
<p>加入验证后，<a href="#listing-name-presence-test">代码清单 6.7</a> 中的测试应该可以通过了：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 6.10</span>：<strong class="green">GREEN</strong></h5>
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake <span class="nb">test</span>:models
</pre></div>
</div>
<p>按照<a href="#listing-name-presence-test">代码清单 6.7</a> 的方式，再编写一个检查 <code>email</code> 属性存在性的测试就简单了，如<a href="#listing-email-presence-test">代码清单 6.11</a> 所示。让这个测试通过的应用代码如<a href="#listing-validates-presence-of-email">代码清单 6.12</a> 所示。</p>
<div id="listing-email-presence-test" data-type="listing">
<h5><span class="title-label">代码清单 6.11</span>：测试 <code>email</code> 属性的验证措施 <span class="red">RED</span></h5>
<div class="source-file">test/models/user_test.rb</div>
<div class="highlight language-ruby"><pre><span class="nb">require</span> <span class="s1">'test_helper'</span>
<span class="k">class</span> <span class="nc">UserTest</span> <span class="o"><</span> <span class="no">ActiveSupport</span><span class="o">::</span><span class="no">TestCase</span>
<span class="k">def</span> <span class="nf">setup</span>
<span class="vi">@user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"Example User"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="k">end</span>
<span class="nb">test</span> <span class="s2">"should be valid"</span> <span class="k">do</span>
<span class="n">assert</span> <span class="vi">@user</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="nb">test</span> <span class="s2">"name should be present"</span> <span class="k">do</span>
<span class="vi">@user</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="s2">""</span>
<span class="n">assert_not</span> <span class="vi">@user</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="hll"> <span class="nb">test</span> <span class="s2">"email should be present"</span> <span class="k">do</span>
</span><span class="hll"> <span class="vi">@user</span><span class="o">.</span><span class="n">email</span> <span class="o">=</span> <span class="s2">" "</span>
</span><span class="hll"> <span class="n">assert_not</span> <span class="vi">@user</span><span class="o">.</span><span class="n">valid?</span>
</span><span class="hll"> <span class="k">end</span>
</span><span class="k">end</span>
</pre></div>
</div>
<div id="listing-validates-presence-of-email" data-type="listing">
<h5><span class="title-label">代码清单 6.12</span>：添加 <code>email</code> 属性存在性验证 <span class="green">GREEN</span></h5>
<div class="source-file">app/models/user.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">User</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Base</span>
<span class="n">validates</span> <span class="ss">:name</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span>
<span class="hll"> <span class="n">validates</span> <span class="ss">:email</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span>
</span><span class="k">end</span>
</pre></div>
</div>
<p>现在，存在性验证都添加了，测试组件应该可以通过了：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 6.13</span>：<strong class="green">GREEN</strong></h5>
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake <span class="nb">test</span>
</pre></div>
</div>
</section>
<section data-type="sect2" id="length-validation">
<h2><span class="title-label">6.2.3</span> 长度验证</h2>
<p>我们已经对用户模型可接受的数据做了一些限制，现在必须为用户提供一个名字，不过我们应该做进一步限制，因为用户的名字会在演示应用中显示，所以最好限制它的长度。有了前一节的基础，这一步就简单了。</p>
<p>没有科学的方法确定最大长度是多少，我们就使用 50 作为长度的上限吧，所以要验证 51 个字符超长了。而且，用户的电子邮件地址可能会超过字符串的最大长度限制，这个最大值在很多数据库中都是 255——这种情况虽然很少发生，但也有发生的可能。因为下一节的格式验证无法实现这种限制，所以我们要在这一节实现。测试如<a href="#listing-length-validation-test">代码清单 6.14</a> 所示。</p>
<div id="listing-length-validation-test" data-type="listing">
<h5><span class="title-label">代码清单 6.14</span>：测试 <code>name</code> 属性的长度验证 <span class="red">RED</span></h5>
<div class="source-file">test/models/user_test.rb</div>
<div class="highlight language-ruby"><pre><span class="nb">require</span> <span class="s1">'test_helper'</span>
<span class="k">class</span> <span class="nc">UserTest</span> <span class="o"><</span> <span class="no">ActiveSupport</span><span class="o">::</span><span class="no">TestCase</span>
<span class="k">def</span> <span class="nf">setup</span>
<span class="vi">@user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"Example User"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="k">end</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="nb">test</span> <span class="s2">"name should not be too long"</span> <span class="k">do</span>
<span class="vi">@user</span><span class="o">.</span><span class="n">name</span> <span class="o">=</span> <span class="s2">"a"</span> <span class="o">*</span> <span class="mi">51</span>
<span class="n">assert_not</span> <span class="vi">@user</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="nb">test</span> <span class="s2">"email should not be too long"</span> <span class="k">do</span>
<span class="vi">@user</span><span class="o">.</span><span class="n">email</span> <span class="o">=</span> <span class="s2">"a"</span> <span class="o">*</span> <span class="mi">244</span> <span class="o">+</span> <span class="s2">"@example.com"</span>
<span class="n">assert_not</span> <span class="vi">@user</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="k">end</span>
</pre></div>
</div>
<p>为了方便，我们使用字符串连乘生成了一个有 51 个字符的字符串。在控制台中可以看到连乘是什么：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="s2">"a"</span> <span class="o">*</span> <span class="mi">51</span>
<span class="go">=> "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"</span>
<span class="gp">>> </span><span class="p">(</span><span class="s2">"a"</span> <span class="o">*</span> <span class="mi">51</span><span class="p">)</span><span class="o">.</span><span class="n">length</span>
<span class="go">=> 51</span>
</pre></div>
</div>
<p>在电子邮件地址长度的测试中，我们创建了一个比要求多一个字符的地址：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="s2">"a"</span> <span class="o">*</span> <span class="mi">244</span> <span class="o">+</span> <span class="s2">"@example.com"</span>
<span class="go">=> "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa</span>
<span class="go">aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa</span>
<span class="go">aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa</span>
<span class="go">[email protected]"</span>
<span class="gp">>> </span><span class="p">(</span><span class="s2">"a"</span> <span class="o">*</span> <span class="mi">244</span> <span class="o">+</span> <span class="s2">"@example.com"</span><span class="p">)</span><span class="o">.</span><span class="n">length</span>
<span class="go">=> 256</span>
</pre></div>
</div>
<p>现在，<a href="#listing-length-validation-test">代码清单 6.14</a> 中的测试应该失败：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 6.15</span>：<strong class="red">RED</strong></h5>
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake <span class="nb">test</span>
</pre></div>
</div>
<p>为了让测试通过，我们要使用验证参数限制长度，即 <code>length</code>，以及限制上线的 <code>maximum</code> 参数，如<a href="#listing-length-validation">代码清单 6.16</a> 所示。</p>
<div id="listing-length-validation" data-type="listing">
<h5><span class="title-label">代码清单 6.16</span>：为 <code>name</code> 属性添加长度验证 <span class="green">GREEN</span></h5>
<div class="source-file">app/models/user.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">User</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Base</span>
<span class="hll"> <span class="n">validates</span> <span class="ss">:name</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span><span class="p">,</span> <span class="ss">length</span><span class="p">:</span> <span class="p">{</span> <span class="ss">maximum</span><span class="p">:</span> <span class="mi">50</span> <span class="p">}</span>
</span> <span class="n">validates</span> <span class="ss">:email</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span><span class="p">,</span> <span class="ss">length</span><span class="p">:</span> <span class="p">{</span> <span class="ss">maximum</span><span class="p">:</span> <span class="mi">255</span> <span class="p">}</span>
<span class="k">end</span>
</pre></div>
</div>
<p>现在测试应该可以通过了：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 6.17</span>：<strong class="green">GREEN</strong></h5>
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake <span class="nb">test</span>
</pre></div>
</div>
<p>测试组件再次通过，接下来我们要实现一个更有挑战的验证——电子邮件地址的格式。</p>
</section>
<section data-type="sect2" id="format-validation">
<h2><span class="title-label">6.2.4</span> 格式验证</h2>
<p><code>name</code> 属性的验证只需做一些简单的限制就好——任何非空、长度小于 51 个字符的字符串都可以。可是 <code>email</code> 属性需要更复杂的限制，必须是有效地电子邮件地址才行。目前我们只拒绝空电子邮件地址，本节我们要限制电子邮件地址符合常用的形式，类似 <code>[email protected]</code> 这种。</p>
<p>这里我们用到的测试和验证不是十全十美的，只是刚好可以覆盖大多数有效的电子邮件地址，并拒绝大多数无效的电子邮件地址。我们会先测试一组有效的电子邮件地址和一组无效的电子邮件地址。我们要使用 <code>%w[]</code> 创建这两组地址，其中每个地址都是字符串形式，如下面的控制台会话所示：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="sx">%w[foo bar baz]</span>
<span class="go">=> ["foo", "bar", "baz"]</span>
<span class="gp">>> </span><span class="n">addresses</span> <span class="o">=</span> <span class="sx">%w[[email protected] [email protected] [email protected]]</span>
<span class="gp">>> </span><span class="n">addresses</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">address</span><span class="o">|</span>
<span class="gp">?> </span> <span class="nb">puts</span> <span class="n">address</span>
<span class="gp">>> </span><span class="k">end</span>
<span class="go">[email protected]</span>
<span class="go">[email protected]</span>
<span class="go">[email protected]</span>
</pre></div>
</div>
<p>在上面这个控制台会话中，我们使用 <code>each</code> 方法（<a href="chapter4.html#blocks">4.3.2 节</a>）遍历 <code>addresses</code> 数组中的元素。掌握这种用法之后，我们就可以编写一些基本的电子邮件地址格式验证测试了。</p>
<p>电子邮件地址格式认证有点棘手，且容易出错，所以我们会先编写检查有效电子邮件地址的测试，这些测试应该能通过，以此捕获验证可能出现的错误。也就是说，添加验证后，不仅要拒绝无效的电子邮件地址，例如 <em>user@example,com</em>，还得接受有效的电子邮件地址，例如 <em>[email protected]</em>。（显然目前会接受所有电子邮件地址，因为只要不为空值都能通过验证。）检查有效电子邮件地址的测试如<a href="#listing-email-format-valid-tests">代码清单 6.18</a> 所示。</p>
<div id="listing-email-format-valid-tests" data-type="listing">
<h5><span class="title-label">代码清单 6.18</span>：测试有效的电子邮件地址格式 <span class="green">GREEN</span></h5>
<div class="source-file">test/models/user_test.rb</div>
<div class="highlight language-ruby"><pre><span class="nb">require</span> <span class="s1">'test_helper'</span>
<span class="k">class</span> <span class="nc">UserTest</span> <span class="o"><</span> <span class="no">ActiveSupport</span><span class="o">::</span><span class="no">TestCase</span>
<span class="k">def</span> <span class="nf">setup</span>
<span class="vi">@user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"Example User"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="k">end</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="nb">test</span> <span class="s2">"email validation should accept valid addresses"</span> <span class="k">do</span>
<span class="n">valid_addresses</span> <span class="o">=</span> <span class="sx">%w[[email protected] [email protected] [email protected]</span>
<span class="sx"> [email protected] [email protected]]</span>
<span class="n">valid_addresses</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">valid_address</span><span class="o">|</span>
<span class="vi">@user</span><span class="o">.</span><span class="n">email</span> <span class="o">=</span> <span class="n">valid_address</span>
<span class="n">assert</span> <span class="vi">@user</span><span class="o">.</span><span class="n">valid?</span><span class="p">,</span> <span class="s2">"</span><span class="si">#{</span><span class="n">valid_address</span><span class="o">.</span><span class="n">inspect</span><span class="si">}</span><span class="s2"> should be valid"</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">end</span>
</pre></div>
</div>
<p>注意，我们为 <code>assert</code> 方法指定了可选的第二个参数，定制错误消息，识别是哪个地址导致测试失败的：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="n">assert</span> <span class="vi">@user</span><span class="o">.</span><span class="n">valid?</span><span class="p">,</span> <span class="s2">"</span><span class="si">#{</span><span class="n">valid_address</span><span class="o">.</span><span class="n">inspect</span><span class="si">}</span><span class="s2"> should be valid"</span>
</pre></div>
</div>
<p>这行代码在字符串插值中使用了 <a href="chapter4.html#hashes-and-symbols">4.3.3 节</a> 介绍的 <code>inspect</code> 方法。像这种使用 <code>each</code> 的测试，最好能知道是哪个地址导致失败的，因为不管哪个地址导致测试失败，都无法看到行号，很难查出问题的根源。</p>
<p>接下来，我们要测试一系列无效的电子邮件，确认它们无法通过验证，例如 <em>user@example,com</em>（点号变成了逗号）和 <em>user_at_foo.org</em>（没有“@”符号）。和<a href="#listing-email-format-valid-tests">代码清单 6.18</a> 一样，<a href="#listing-email-format-validation-tests">代码清单 6.19</a> 中也指定了错误消息参数，识别是哪个地址导致测试失败的。</p>
<div id="listing-email-format-validation-tests" data-type="listing">
<h5><span class="title-label">代码清单 6.19</span>：测试电子邮件地址格式验证 <span class="red">RED</span></h5>
<div class="source-file">test/models/user_test.rb</div>
<div class="highlight language-ruby"><pre><span class="nb">require</span> <span class="s1">'test_helper'</span>
<span class="k">class</span> <span class="nc">UserTest</span> <span class="o"><</span> <span class="no">ActiveSupport</span><span class="o">::</span><span class="no">TestCase</span>
<span class="k">def</span> <span class="nf">setup</span>
<span class="vi">@user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"Example User"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="k">end</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="nb">test</span> <span class="s2">"email validation should reject invalid addresses"</span> <span class="k">do</span>
<span class="n">invalid_addresses</span> <span class="o">=</span> <span class="sx">%w[user@example,com user_at_foo.org user.name@example.</span>
<span class="sx"> foo@bar_baz.com foo@bar+baz.com]</span>
<span class="n">invalid_addresses</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">invalid_address</span><span class="o">|</span>
<span class="vi">@user</span><span class="o">.</span><span class="n">email</span> <span class="o">=</span> <span class="n">invalid_address</span>
<span class="n">assert_not</span> <span class="vi">@user</span><span class="o">.</span><span class="n">valid?</span><span class="p">,</span> <span class="s2">"</span><span class="si">#{</span><span class="n">invalid_address</span><span class="o">.</span><span class="n">inspect</span><span class="si">}</span><span class="s2"> should be invalid"</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">end</span>
</pre></div>
</div>
<p>现在，测试应该失败：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 6.20</span>：<strong class="red">RED</strong></h5>
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake <span class="nb">test</span>
</pre></div>
</div>
<p>电子邮件地址格式验证使用 <code>format</code> 参数，用法如下：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="n">validates</span> <span class="ss">:email</span><span class="p">,</span> <span class="nb">format</span><span class="p">:</span> <span class="p">{</span> <span class="ss">with</span><span class="p">:</span> <span class="sr">/<regular expression>/</span> <span class="p">}</span>
</pre></div>
</div>
<p>使用指定的正则表达式验证属性。正则表达式很强大，但往往很晦涩，用来模式匹配字符串。所以我们要编写一个正则表达式，匹配有效的电子邮件地址，但不匹配无效的地址。</p>
<p>在官方标准中其实有一个正则表达式，可以匹配全部有效的电子邮件地址，但没必要使用这么复杂的正则表达式。<sup>[<a id="fn-ref-11" href="#fn-11">11</a>]</sup>本书使用一个更务实的正则表达式，能很好地满足实际需求，如下所示：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="no">VALID_EMAIL_REGEX</span> <span class="o">=</span> <span class="sr">/\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i</span>
</pre></div>
</div>
<p>为了便于理解，我把 <code>VALID_EMAIL_REGEX</code> 拆分成几块来讲，如<a href="#table-valid-email-regex">表 6.1</a> 所示。</p>
<table id="table-valid-email-regex" class="tableblock frame-all grid-all" style="width: 100%;">
<caption><span class="title-label">表 6.1</span>：拆解匹配有效电子邮件地址的正则表达式</caption>
<colgroup>
<col style="width: 50%;" />
<col style="width: 50%;" />
</colgroup>
<thead>
<tr>
<th class="tableblock halign-left valign-top">表达式</th>
<th class="tableblock halign-left valign-top">含义</th>
</tr>
</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>/\A[\w+\-.]@[a-z\d\-.]\.[a-z]+\z/i</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">完整的正则表达式</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>/</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">正则表达式开始</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>\A</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">匹配字符串的开头</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>[\w+\-.]+</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">一个或多个字母、加号、连字符、或点号</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>@</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">匹配 @ 符号</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>[a-z\d\-.]+</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">一个或多个字母、数字、连字符或点号</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>\.</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">匹配点号</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>[a-z]+</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">一个或多个字母</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>\z</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">匹配字符串结尾</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>/</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">结束正则表达式</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>i</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">不区分大小写</p></td>
</tr>
</tbody>
</table>
<p>从<a href="#table-valid-email-regex">表 6.1</a> 中虽然能学到很多，但若想真正理解正则表达式，我觉得交互式正则表达式匹配程序，例如 <a href="http://www.rubular.com/">Rubular</a>（<a href="#fig-rubular">图 6.6</a>）<sup>[<a id="fn-ref-12" href="#fn-12">12</a>]</sup>，是必不可少的的。Rubular 的界面很友好，便于编写所需的正则表达式，而且还有一个便捷的语法速查表。我建议你使用 Rubular 来理解<a href="#table-valid-email-regex">表 6.1</a>中的正则表达式——读得次数再多也不比不上在 Rubular 中实操几次。（注意：如果你在 Rubular 中输入<a href="#table-valid-email-regex">表 6.1</a> 中的正则表达式，要把 <code>\A</code> 和 <code>\z</code> 去掉，因为 Rubular 无法正确处理字符串的头尾。）</p>
<div id="fig-rubular" class="figure"><img src="images/chapter6/rubular.png" alt="rubular" /><div class="figcaption"><span class="title-label">图 6.6</span>：强大的 Rubular 正则表达式编辑器</div></div>
<p>在 <code>email</code> 属性的格式验证中使用这个表达式后得到的代码如<a href="#listing-validates-format-of-email">代码清单 6.21</a> 所示。</p>
<div id="listing-validates-format-of-email" data-type="listing">
<h5><span class="title-label">代码清单 6.21</span>：使用正则表达式验证电子邮件地址的格式 <span class="green">GREEN</span></h5>
<div class="source-file">app/models/user.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">User</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Base</span>
<span class="n">validates</span> <span class="ss">:name</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span><span class="p">,</span> <span class="ss">length</span><span class="p">:</span> <span class="p">{</span> <span class="ss">maximum</span><span class="p">:</span> <span class="mi">50</span> <span class="p">}</span>
<span class="hll"> <span class="no">VALID_EMAIL_REGEX</span> <span class="o">=</span> <span class="sr">/\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i</span>
</span> <span class="n">validates</span> <span class="ss">:email</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span><span class="p">,</span> <span class="ss">length</span><span class="p">:</span> <span class="p">{</span> <span class="ss">maximum</span><span class="p">:</span> <span class="mi">255</span> <span class="p">},</span>
<span class="hll"> <span class="nb">format</span><span class="p">:</span> <span class="p">{</span> <span class="ss">with</span><span class="p">:</span> <span class="no">VALID_EMAIL_REGEX</span> <span class="p">}</span>
</span><span class="k">end</span>
</pre></div>
</div>
<p>其中，<code>VALID_EMAIL_REGEX</code> 是一个常量，在 Ruby 中常量的首字母为大写形式。这段代码：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="no">VALID_EMAIL_REGEX</span> <span class="o">=</span> <span class="sr">/\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i</span>
<span class="n">validates</span> <span class="ss">:email</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span><span class="p">,</span> <span class="ss">length</span><span class="p">:</span> <span class="p">{</span> <span class="ss">maximum</span><span class="p">:</span> <span class="mi">255</span> <span class="p">},</span>
<span class="nb">format</span><span class="p">:</span> <span class="p">{</span> <span class="ss">with</span><span class="p">:</span> <span class="no">VALID_EMAIL_REGEX</span> <span class="p">}</span>
</pre></div>
</div>
<p>确保只有匹配正则表达式的电子邮件地址才是有效的。这个正则表达式有一个缺陷：能匹配 <code>[email protected]</code> 这种有连续点号的地址。修正这个瑕疵需要一个更复杂的正则表达式，留作练习由你完成（<a href="#modeling-users-exercises">6.5 节</a>）。</p>
<p>现在测试应该可以通过了：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 6.22</span>：<strong class="green">GREEN</strong></h5>
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake <span class="nb">test</span>:models
</pre></div>
</div>
<p>那么就只剩一个限制要实现了：确保电子邮件地址的唯一性。</p>
</section>
<section data-type="sect2" id="uniqueness-validation">
<h2><span class="title-label">6.2.5</span> 唯一性验证</h2>
<p>确保电子邮件地址的唯一性（这样才能作为用户名），要使用 <code>validates</code> 方法的 <code>:unique</code> 参数。提前说明，实现的过程中有一个很大的陷阱，所以不要轻易跳过本节，要认真阅读。</p>
<p>我们要先编写一些简短的测试。之前的模型测试，只是使用 <code>User.new</code> 在内存中创建一个 Ruby 对象，但是测试唯一性时要把数据存入数据库。<sup>[<a id="fn-ref-13" href="#fn-13">13</a>]</sup>对重复电子邮件地址的测试如<a href="#listing-validates-uniqueness-of-email-test">代码清单 6.23</a> 所示。</p>
<div id="listing-validates-uniqueness-of-email-test" data-type="listing">
<h5><span class="title-label">代码清单 6.23</span>：拒绝重复电子邮件地址的测试 <span class="red">RED</span></h5>
<div class="source-file">test/models/user_test.rb</div>
<div class="highlight language-ruby"><pre><span class="nb">require</span> <span class="s1">'test_helper'</span>
<span class="k">class</span> <span class="nc">UserTest</span> <span class="o"><</span> <span class="no">ActiveSupport</span><span class="o">::</span><span class="no">TestCase</span>
<span class="k">def</span> <span class="nf">setup</span>
<span class="vi">@user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"Example User"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="k">end</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="hll"> <span class="nb">test</span> <span class="s2">"email addresses should be unique"</span> <span class="k">do</span>
</span><span class="hll"> <span class="n">duplicate_user</span> <span class="o">=</span> <span class="vi">@user</span><span class="o">.</span><span class="n">dup</span>
</span><span class="hll"> <span class="vi">@user</span><span class="o">.</span><span class="n">save</span>
</span><span class="hll"> <span class="n">assert_not</span> <span class="n">duplicate_user</span><span class="o">.</span><span class="n">valid?</span>
</span><span class="hll"> <span class="k">end</span>
</span><span class="k">end</span>
</pre></div>
</div>
<p>我们使用 <code>@user.dup</code> 方法创建一个和 <code>@user</code> 的电子邮件地址一样的用户对象，然后保存 <code>@user</code>，因为数据库中的 <code>@user</code> 已经占用了这个电子邮件地址，所有 <code>duplicate_user</code> 对象无效。</p>
<p>在 <code>email</code> 属性的验证中加入 <code>uniqueness: true</code> 可以让<a href="#listing-validates-uniqueness-of-email-test">代码清单 6.23</a> 中的测试通过，如<a href="#listing-validates-uniqueness-of-email">代码清单 6.24</a> 所示。</p>
<div id="listing-validates-uniqueness-of-email" data-type="listing">
<h5><span class="title-label">代码清单 6.24</span>：电子邮件地址唯一性验证 <span class="green">GREEN</span></h5>
<div class="source-file">app/models/user.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">User</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Base</span>
<span class="n">validates</span> <span class="ss">:name</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span><span class="p">,</span> <span class="ss">length</span><span class="p">:</span> <span class="p">{</span> <span class="ss">maximum</span><span class="p">:</span> <span class="mi">50</span> <span class="p">}</span>
<span class="no">VALID_EMAIL_REGEX</span> <span class="o">=</span> <span class="sr">/\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i</span>
<span class="n">validates</span> <span class="ss">:email</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span><span class="p">,</span> <span class="ss">length</span><span class="p">:</span> <span class="p">{</span> <span class="ss">maximum</span><span class="p">:</span> <span class="mi">255</span> <span class="p">},</span>
<span class="nb">format</span><span class="p">:</span> <span class="p">{</span> <span class="ss">with</span><span class="p">:</span> <span class="no">VALID_EMAIL_REGEX</span> <span class="p">},</span>
<span class="hll"> <span class="ss">uniqueness</span><span class="p">:</span> <span class="kp">true</span>
</span><span class="k">end</span>
</pre></div>
</div>
<p>这还不行，一般来说电子邮件地址不区分大小写，也就说 <code>[email protected]</code> 和 <code>[email protected]</code> 或 <code>[email protected]</code> 是同一个地址，所以验证时也要考虑这种情况。<sup>[<a id="fn-ref-14" href="#fn-14">14</a>]</sup>因此，还要测试不区分大小写，如<a href="#listing-validates-uniqueness-of-email-case-insensitive-test">代码清单 6.25</a> 所示。</p>
<div id="listing-validates-uniqueness-of-email-case-insensitive-test" data-type="listing">
<h5><span class="title-label">代码清单 6.25</span>：测试电子邮件地址的唯一性验证不区分大小写 <span class="red">RED</span></h5>
<div class="source-file">test/models/user_test.rb</div>
<div class="highlight language-ruby"><pre><span class="nb">require</span> <span class="s1">'test_helper'</span>
<span class="k">class</span> <span class="nc">UserTest</span> <span class="o"><</span> <span class="no">ActiveSupport</span><span class="o">::</span><span class="no">TestCase</span>
<span class="k">def</span> <span class="nf">setup</span>
<span class="vi">@user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"Example User"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="k">end</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="nb">test</span> <span class="s2">"email addresses should be unique"</span> <span class="k">do</span>
<span class="n">duplicate_user</span> <span class="o">=</span> <span class="vi">@user</span><span class="o">.</span><span class="n">dup</span>
<span class="hll"> <span class="n">duplicate_user</span><span class="o">.</span><span class="n">email</span> <span class="o">=</span> <span class="vi">@user</span><span class="o">.</span><span class="n">email</span><span class="o">.</span><span class="n">upcase</span>
</span> <span class="vi">@user</span><span class="o">.</span><span class="n">save</span>
<span class="n">assert_not</span> <span class="n">duplicate_user</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="k">end</span>
</pre></div>
</div>
<p>上面的代码，在字符串上调用 <code>upcase</code> 方法（<a href="chapter4.html#blocks">4.3.2 节</a>简介过）。这个测试和前面对重复电子邮件的测试作用一样，只是把地址转换成全部大写字母的形式。如果觉得太抽象，那就在控制台中实操一下吧：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="go">$ rails console --sandbox</span>
<span class="gp">>> </span><span class="n">user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="nb">name</span><span class="p">:</span> <span class="s2">"Example User"</span><span class="p">,</span> <span class="ss">email</span><span class="p">:</span> <span class="s2">"[email protected]"</span><span class="p">)</span>
<span class="gp">>> </span><span class="n">user</span><span class="o">.</span><span class="n">email</span><span class="o">.</span><span class="n">upcase</span>
<span class="go">=> "[email protected]"</span>
<span class="gp">>> </span><span class="n">duplicate_user</span> <span class="o">=</span> <span class="n">user</span><span class="o">.</span><span class="n">dup</span>
<span class="gp">>> </span><span class="n">duplicate_user</span><span class="o">.</span><span class="n">email</span> <span class="o">=</span> <span class="n">user</span><span class="o">.</span><span class="n">email</span><span class="o">.</span><span class="n">upcase</span>
<span class="gp">>> </span><span class="n">duplicate_user</span><span class="o">.</span><span class="n">valid?</span>
<span class="go">=> true</span>
</pre></div>
</div>
<p>当然，现在 <code>duplicate_user.valid?</code> 的返回值是 <code>true</code>，因为唯一性验证还区分大小写。我们希望得到的结果是 <code>false</code>。幸好 <code>:uniqueness</code> 可以指定 <code>:case_sensitive</code> 选项，正好可以解决这个问题，如<a href="#listing-validates-uniqueness-of-email-case-insensitive">代码清单 6.26</a> 所示。</p>
<div id="listing-validates-uniqueness-of-email-case-insensitive" data-type="listing">
<h5><span class="title-label">代码清单 6.26</span>：电子邮件地址唯一性验证，不区分大小写 <span class="green">GREEN</span></h5>
<div class="source-file">app/models/user.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">User</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Base</span>
<span class="n">validates</span> <span class="ss">:name</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span><span class="p">,</span> <span class="ss">length</span><span class="p">:</span> <span class="p">{</span> <span class="ss">maximum</span><span class="p">:</span> <span class="mi">50</span> <span class="p">}</span>
<span class="no">VALID_EMAIL_REGEX</span> <span class="o">=</span> <span class="sr">/\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i</span>
<span class="n">validates</span> <span class="ss">:email</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span><span class="p">,</span> <span class="ss">length</span><span class="p">:</span> <span class="p">{</span> <span class="ss">maximum</span><span class="p">:</span> <span class="mi">255</span> <span class="p">},</span>
<span class="nb">format</span><span class="p">:</span> <span class="p">{</span> <span class="ss">with</span><span class="p">:</span> <span class="no">VALID_EMAIL_REGEX</span> <span class="p">},</span>
<span class="hll"> <span class="ss">uniqueness</span><span class="p">:</span> <span class="p">{</span> <span class="ss">case_sensitive</span><span class="p">:</span> <span class="kp">false</span> <span class="p">}</span>
</span><span class="k">end</span>
</pre></div>
</div>
<p>注意，我们直接把 <code>true</code> 换成了 <code>case_sensitive: false</code>，Rails 会自动指定 <code>:uniqueness</code> 的值为 <code>true</code>。</p>
<p>至此，我们的应用虽还有不足，但基本可以保证电子邮件地址的唯一性了，测试组件应该可以通过了：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 6.27</span>：<strong class="green">GREEN</strong></h5>
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake <span class="nb">test</span>
</pre></div>
</div>
<p>现在还有一个小问题——Active Record 中的唯一性验证无法保证数据库层也能实现唯一性。我来解释一下：</p>
<ol class="arabic">
<li>
<p>Alice 使用 [email protected] 在演示应用中注册；</p>
</li>
<li>
<p>Alice 不小心按了两次提交按钮，连续发送了两次请求；</p>
</li>
<li>
<p>然后就会发生这种事情：请求 1 在内存中新建了一个用户对象，能通过验证；请求 2 也一样。请求 1 创建的用户存入了数据库，请求 2 创建的用户也存入了数据库。</p>
</li>
<li>
<p>结果是，尽管有唯一性验证，数据库中还是有两条用户记录的电子邮件地址是一样的。</p>
</li>