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<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8"/>
<title>Ruby on Rails 教程 - 第 11 章 用户的微博</title>
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<article class="article">
<section data-type="chapter" id="user-microposts">
<h1><span class="title-label">第 11 章</span> 用户的微博</h1>
<p>在开发这个演示应用的过程中，我们用到了四个资源：用户，会话，账户激活和密码重设。但只有第一个资源通过 Active Record 模型对应了数据库中的表。本章，我们要再实现一个这样的资源——用户的微博，即用户发布的短消息。<a href="chapter2.html#a-toy-app">第 2 章</a>实现了微博的雏形，本章则会在 <a href="chapter2.html#the-microposts-resource">2.3 节</a>的基础上，实现一个功能完整的微博资源。首先，我们要创建微博数据模型，通过 <code>has_many</code> 和 <code>belongs_to</code> 方法把微博和用户关联起来，然后再创建处理和显示微博所需的表单及局部视图（<a href="#micropost-images">11.4 节</a>还要实现上传图片功能）。在<a href="chapter12.html#following-users">第 12 章</a>，还要加入关注其他用户的功能，届时，我们这个山寨版 Twitter 才算完成。</p>
<section data-type="sect1" id="a-micropost-model">
<h1><span class="title-label">11.1</span> 微博模型</h1>
<p>实现微博资源的第一步是创建微博数据模型，在模型中设定微博的基本特征。和 <a href="chapter2.html#the-microposts-resource">2.3 节</a>创建的模型类似，我们要实现的微博模型要包含数据验证，以及和用户模型之间的关联。除此之外，我们还会做充分的测试，指定默认的排序方式，以及自动删除已注销用户的微博。</p>
<p>如果使用 Git 做版本控制的话，和之前一样，建议你新建一个主题分支：</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 user-microposts
</pre></div>
</div>
<section data-type="sect2" id="the-basic-model">
<h2><span class="title-label">11.1.1</span> 基本模型</h2>
<p>微博模型只需要两个属性：一个是 <code>content</code>，用来保存微博的内容；另一个是 <code>user_id</code>，把微博和用户关联起来。微博模型的结构如<a href="#fig-micropost-model">图 11.1</a> 所示。</p>
<div id="fig-micropost-model" class="figure"><img src="images/chapter11/micropost_model_3rd_edition.png" alt="micropost model 3rd edition" /><div class="figcaption"><span class="title-label">图 11.1</span>：微博数据模型</div></div>
<p>注意，在这个模型中，<code>content</code> 属性的类型为 <code>text</code>，而不是 <code>string</code>，目的是存储任意长度的文本。虽然我们会限制微博内容的长度不超过 140 个字符（<a href="#micropost-validations">11.1.2 节</a>），也就是说在 <code>string</code> 类型的 255 个字符长度的限制内，但使用 <code>text</code> 能更好地表达微博的特性，即把微博看成一段文本更符合常理。在 <a href="#creating-microposts">11.3.2 节</a>，会把文本字段换成多行文本字段，用于提交微博。而且，如果以后想让微博的内容更长一些（例如包含多国文字），使用 <code>text</code> 类型处理起来更灵活。何况，在生产环境中使用 <code>text</code> 类型并<a href="http://www.postgresql.org/docs/9.1/static/datatype-character.html">没有什么性能差异</a>，所以不会有什么额外消耗。</p>
<p>和用户模型一样（<a href="chapter6.html#listing-generate-user-model">代码清单 6.1</a>），我们要使用 <code>generate model</code> 命令生成微博模型：</p>
<div data-type="listing">
<div class="highlight language-sh"><pre><span class="nv">$ </span>rails generate model Micropost content:text user:references
</pre></div>
</div>
<p>这个命令会生成一个迁移文件，用于在数据库中生成一个名为 <code>microposts</code> 的表，如<a href="#listing-micropost-migration">代码清单 11.1</a> 所示。可以和生成 <code>users</code> 表的迁移对照一下，参见<a href="chapter6.html#listing-users-migration">代码清单 6.2</a>。二者之间最大的区别是，前者使用了 <code>references</code> 类型。<code>references</code> 会自动添加 <code>user_id</code> 列（以及索引），把用户和微博关联起来。和用户模型一样，微博模型的迁移中也自动生成了 <code>t.timestamps</code>。<a href="chapter6.html#database-migrations">6.1.1 节</a>说过，这行代码的作用是添加 <code>created_at</code> 和 <code>updated_at</code> 两列。（<a href="#micropost-refinements">11.1.4 节</a>和 <a href="#rendering-microposts">11.2.1 节</a>会使用 <code>created_at</code> 列。）</p>
<div id="listing-micropost-migration" data-type="listing">
<h5><span class="title-label">代码清单 11.1</span>：微博模型的迁移文件，还创建了索引</h5>
<div class="source-file">db/migrate/[timestamp]_create_microposts.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">CreateMicroposts</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">:microposts</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">text</span> <span class="ss">:content</span>
<span class="n">t</span><span class="o">.</span><span class="n">references</span> <span class="ss">:user</span><span class="p">,</span> <span class="ss">index</span><span class="p">:</span> <span class="kp">true</span><span class="p">,</span> <span class="ss">foreign_key</span><span class="p">:</span> <span class="kp">true</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="hll"> <span class="n">add_index</span> <span class="ss">:microposts</span><span class="p">,</span> <span class="o">[</span><span class="ss">:user_id</span><span class="p">,</span> <span class="ss">:created_at</span><span class="o">]</span>
</span> <span class="k">end</span>
<span class="k">end</span>
</pre></div>
</div>
<p>因为我们会按照发布时间的倒序查询某个用户发布的所有微博，所以在上述代码中为 <code>user_id</code> 和 <code>created_at</code> 列创建了索引（参见<a href="chapter6.html#aside-database-indices">旁注 6.2</a>）：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="n">add_index</span> <span class="ss">:microposts</span><span class="p">,</span> <span class="o">[</span><span class="ss">:user_id</span><span class="p">,</span> <span class="ss">:created_at</span><span class="o">]</span>
</pre></div>
</div>
<p>我们把 <code>user_id</code> 和 <code>created_at</code> 放在一个数组中，告诉 Rails 我们要创建的是“多键索引”（multiple key index），因此 Active Record 会同时使用这两个键。</p>
<p>然后像之前一样，执行下面的命令更新数据库：</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="micropost-validations">
<h2><span class="title-label">11.1.2</span> 微博模型的数据验证</h2>
<p>我们已经创建了基本的数据模型，下面要添加一些验证，实现符合需求的约束。微博模型必须要有一个属性表示用户的 ID，这样才能知道某篇微博是由哪个用户发布的。实现这样的属性，最好的方法是使用 Active Record 关联。<a href="#user-micropost-associations">11.1.3 节</a>会实现关联，现在我们直接处理微博模型。</p>
<p>我们可以参照用户模型的测试（<a href="chapter6.html#listing-name-presence-test">代码清单 6.7</a>），在 <code>setup</code> 方法中新建一个微博对象，并把它和固件中的一个有效用户关联起来，然后在测试中检查这个微博对象是否有效。因为每篇微博都要和用户关联起来，所以我们还要为 <code>user_id</code> 属性的存在性验证编写一个测试。综上所述，测试如<a href="#listing-micropost-validity-test">代码清单 11.2</a> 所示。</p>
<div id="listing-micropost-validity-test" data-type="listing">
<h5><span class="title-label">代码清单 11.2</span>：测试微博是否有效 <span class="red">RED</span></h5>
<div class="source-file">test/models/micropost_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">MicropostTest</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="n">users</span><span class="p">(</span><span class="ss">:michael</span><span class="p">)</span>
<span class="hll"> <span class="c1"># 这行代码不符合常见做法</span>
</span><span class="hll"> <span class="vi">@micropost</span> <span class="o">=</span> <span class="no">Micropost</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="ss">content</span><span class="p">:</span> <span class="s2">"Lorem ipsum"</span><span class="p">,</span> <span class="ss">user_id</span><span class="p">:</span> <span class="vi">@user</span><span class="o">.</span><span class="n">id</span><span class="p">)</span>
</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">@micropost</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="nb">test</span> <span class="s2">"user id should be present"</span> <span class="k">do</span>
<span class="vi">@micropost</span><span class="o">.</span><span class="n">user_id</span> <span class="o">=</span> <span class="kp">nil</span>
<span class="n">assert_not</span> <span class="vi">@micropost</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="k">end</span>
</pre></div>
</div>
<p>如 <code>setup</code> 方法中的注释所说，创建微博使用的方法不符合常见做法，我们会在 <a href="#user-micropost-associations">11.1.3 节</a>修正。</p>
<p>微博是否有效的测试能通过，但用户 ID 存在性验证的测试无法通过，因为微博模型目前还没有任何验证规则：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 11.3</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>为了让测试通过，我们要添加用户 ID 存在性验证，如<a href="#listing-micropost-user-id-validation">代码清单 11.4</a> 所示。（注意，这段代码中 <code>belongs_to</code> 那行由<a href="#listing-micropost-migration">代码清单 11.1</a> 中的迁移自动生成。<a href="#user-micropost-associations">11.1.3 节</a>会深入介绍这行代码的作用。）</p>
<div id="listing-micropost-user-id-validation" data-type="listing">
<h5><span class="title-label">代码清单 11.4</span>：微博模型 <code>user_id</code> 属性的验证 <span class="green">GREEN</span></h5>
<div class="source-file">app/models/micropost.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">Micropost</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Base</span>
<span class="n">belongs_to</span> <span class="ss">:user</span>
<span class="hll"> <span class="n">validates</span> <span class="ss">:user_id</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，整个测试组件应该都能通过：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 11.5</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>接下来，我们要为 <code>content</code> 属性加上数据验证（参照 <a href="chapter2.html#putting-the-micro-in-microposts">2.3.2 节</a>的做法）。和 <code>user_id</code> 一样，<code>content</code> 属性必须存在，而且还要限制内容的长度不能超过 140 个字符，这才是真正的“微”博。首先，我们要参照 <a href="chapter6.html#user-validations">6.2 节</a>用户模型的验证测试，编写一些简单的测试，如<a href="#listing-micropost-validations-tests">代码清单 11.6</a> 所示。</p>
<div id="listing-micropost-validations-tests" data-type="listing">
<h5><span class="title-label">代码清单 11.6</span>：测试微博模型的验证 <span class="red">RED</span></h5>
<div class="source-file">test/models/micropost_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">MicropostTest</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="n">users</span><span class="p">(</span><span class="ss">:michael</span><span class="p">)</span>
<span class="vi">@micropost</span> <span class="o">=</span> <span class="no">Micropost</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="ss">content</span><span class="p">:</span> <span class="s2">"Lorem ipsum"</span><span class="p">,</span> <span class="ss">user_id</span><span class="p">:</span> <span class="vi">@user</span><span class="o">.</span><span class="n">id</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">@micropost</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="nb">test</span> <span class="s2">"user id should be present"</span> <span class="k">do</span>
<span class="vi">@micropost</span><span class="o">.</span><span class="n">user_id</span> <span class="o">=</span> <span class="kp">nil</span>
<span class="n">assert_not</span> <span class="vi">@micropost</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">"content should be present"</span> <span class="k">do</span>
</span><span class="hll"> <span class="vi">@micropost</span><span class="o">.</span><span class="n">content</span> <span class="o">=</span> <span class="s2">" "</span>
</span><span class="hll"> <span class="n">assert_not</span> <span class="vi">@micropost</span><span class="o">.</span><span class="n">valid?</span>
</span><span class="hll"> <span class="k">end</span>
</span>
<span class="hll"> <span class="nb">test</span> <span class="s2">"content should be at most 140 characters"</span> <span class="k">do</span>
</span><span class="hll"> <span class="vi">@micropost</span><span class="o">.</span><span class="n">content</span> <span class="o">=</span> <span class="s2">"a"</span> <span class="o">*</span> <span class="mi">141</span>
</span><span class="hll"> <span class="n">assert_not</span> <span class="vi">@micropost</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>和 <a href="chapter6.html#user-validations">6.2 节</a>一样，<a href="#listing-micropost-validations-tests">代码清单 11.6</a>也用到了字符串连乘来测试微博内容长度的验证：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="go">$ rails console</span>
<span class="gp">>> </span><span class="s2">"a"</span> <span class="o">*</span> <span class="mi">10</span>
<span class="go">=> "aaaaaaaaaa"</span>
<span class="gp">>> </span><span class="s2">"a"</span> <span class="o">*</span> <span class="mi">141</span>
<span class="go">=> "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa</span>
<span class="go">aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"</span>
</pre></div>
</div>
<p>在模型中添加的代码基本上和用户模型 <code>name</code> 属性的验证一样（<a href="chapter6.html#listing-length-validation">代码清单 6.16</a>），如<a href="#listing-micropost-validations">代码清单 11.7</a> 所示。</p>
<div id="listing-micropost-validations" data-type="listing">
<h5><span class="title-label">代码清单 11.7</span>：微博模型的验证 <span class="green">GREEN</span></h5>
<div class="source-file">app/models/micropost.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">Micropost</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Base</span>
<span class="n">belongs_to</span> <span class="ss">:user</span>
<span class="n">validates</span> <span class="ss">:user_id</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">:content</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">140</span> <span class="p">}</span>
</span><span class="k">end</span>
</pre></div>
</div>
<p>现在，测试组件应该能通过了：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 11.8</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="user-micropost-associations">
<h2><span class="title-label">11.1.3</span> 用户和微博之间的关联</h2>
<p>为 Web 应用构建数据模型时，最基本的要求是要能够在不同的模型之间建立关联。在这个应用中，每篇微博都属于某个用户，而每个用户一般都有多篇微博。用户和微博之间的关系在 <a href="chapter2.html#a-user-has-many-microposts">2.3.3 节</a>简单介绍过，如<a href="#fig-micropost-belongs-to-user">图 11.2</a> 和<a href="#fig-user-has-many-microposts">图 11.3</a> 所示。在实现这种关联的过程中，我们会为微博模型和用户模型编写一些测试。</p>
<div id="fig-micropost-belongs-to-user" class="figure"><img src="images/chapter11/micropost_belongs_to_user.png" alt="micropost belongs to user" /><div class="figcaption"><span class="title-label">图 11.2</span>：微博和所属用户之间的 <code>belongs_to</code>（属于）关系</div></div>
<div id="fig-user-has-many-microposts" class="figure"><img src="images/chapter11/user_has_many_microposts.png" alt="user has many microposts" /><div class="figcaption"><span class="title-label">图 11.3</span>：用户和微博之间的 <code>has_many</code>（拥有多个）关系</div></div>
<p>使用本节实现的 <code>belongs_to</code>/<code>has_many</code> 关联之后，Rails 会自动创建一些方法，如<a href="#table-association-methods">表 11.1</a> 所示。注意，从表中可知，相较于下面的方法</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="no">Micropost</span><span class="o">.</span><span class="n">create</span>
<span class="no">Micropost</span><span class="o">.</span><span class="n">create!</span>
<span class="no">Micropost</span><span class="o">.</span><span class="n">new</span>
</pre></div>
</div>
<p>我们得到了</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="n">user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">create</span>
<span class="n">user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">create!</span>
<span class="n">user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">build</span>
</pre></div>
</div>
<p>后者才是创建微博的正确方式，即通过相关联的用户对象创建。通过这种方式创建的微博，其 <code>user_id</code> 属性会自动设为正确的值。所以，我们可以把<a href="#listing-micropost-validity-test">代码清单 11.2</a> 中的下述代码</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="vi">@user</span> <span class="o">=</span> <span class="n">users</span><span class="p">(</span><span class="ss">:michael</span><span class="p">)</span>
<span class="c1"># 这行代码不符合常见做法</span>
<span class="vi">@micropost</span> <span class="o">=</span> <span class="no">Micropost</span><span class="o">.</span><span class="n">new</span><span class="p">(</span><span class="ss">content</span><span class="p">:</span> <span class="s2">"Lorem ipsum"</span><span class="p">,</span> <span class="ss">user_id</span><span class="p">:</span> <span class="vi">@user</span><span class="o">.</span><span class="n">id</span><span class="p">)</span>
</pre></div>
</div>
<p>改为</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="vi">@user</span> <span class="o">=</span> <span class="n">users</span><span class="p">(</span><span class="ss">:michael</span><span class="p">)</span>
<span class="vi">@micropost</span> <span class="o">=</span> <span class="vi">@user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">build</span><span class="p">(</span><span class="ss">content</span><span class="p">:</span> <span class="s2">"Lorem ipsum"</span><span class="p">)</span>
</pre></div>
</div>
<p>（和 <code>new</code> 方法一样，<code>build</code> 方法返回一个存储在内存中的对象，不会修改数据库。）只要关联定义的正确，<code>@micropost</code> 变量的 <code>user_id</code> 属性就会自动设为所关联用户的 ID。</p>
<table id="table-association-methods" class="tableblock frame-all grid-all" style="width: 100%;">
<caption><span class="title-label">表 11.1</span>：用户和微博之间建立关联后得到的方法简介</caption>
<colgroup>
<col style="width: 50%;" />
<col style="width: 50%;" />
</colgroup>
<thead>
<tr>
<th class="tableblock halign-left valign-top">方法</th>
<th class="tableblock halign-left valign-top">作用</th>
</tr>
</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>micropost.user</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">返回和微博关联的用户对象</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>user.microposts</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">返回用户发布的所有微博</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>user.microposts.create(arg)</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">创建一篇 <code>user</code> 发布的微博</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>user.microposts.create!(arg)</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">创建一篇 <code>user</code> 发布的微博（失败时抛出异常）</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>user.microposts.build(arg)</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">返回一个 <code>user</code> 发布的新微博对象</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>user.microposts.find_by(id: 1)</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">查找 <code>user</code> 发布的一篇微博，而且微博的 ID 为 1</p></td>
</tr>
</tbody>
</table>
<p>为了让 <code>@user.microposts.build</code> 这样的代码能使用，我们要修改用户模型和微博模型，添加一些代码，把这两个模型关联起来。<a href="#listing-micropost-migration">代码清单 11.1</a> 中的迁移已经自动添加了 <code>belongs_to :user</code>，如<a href="#listing-micropost-belongs-to-user">代码清单 11.9</a> 所示。关联的另一头，<code>has_many :microposts</code>，我们要自己动手添加，如<a href="#listing-user-has-many-microposts">代码清单 11.10</a> 所示。</p>
<div id="listing-micropost-belongs-to-user" data-type="listing">
<h5><span class="title-label">代码清单 11.9</span>：一篇微博属于（<code>belongs_to</code>）一个用户 <span class="green">GREEN</span></h5>
<div class="source-file">app/models/micropost.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">Micropost</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">belongs_to</span> <span class="ss">:user</span>
</span> <span class="n">validates</span> <span class="ss">:user_id</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span>
<span class="n">validates</span> <span class="ss">:content</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">140</span> <span class="p">}</span>
<span class="k">end</span>
</pre></div>
</div>
<div id="listing-user-has-many-microposts" data-type="listing">
<h5><span class="title-label">代码清单 11.10</span>：一个用户有多篇（<code>has_many</code>）微博 <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">has_many</span> <span class="ss">:microposts</span>
</span> <span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="k">end</span>
</pre></div>
</div>
<p>定义好关联后，我们可以修改<a href="#listing-micropost-validity-test">代码清单 11.2</a> 中的 <code>setup</code> 方法了，使用正确的方式创建一个微博对象，如<a href="#listing-micropost-validity-test-idiomatic">代码清单 11.11</a> 所示。</p>
<div id="listing-micropost-validity-test-idiomatic" data-type="listing">
<h5><span class="title-label">代码清单 11.11</span>：使用正确的方式创建微博对象 <span class="green">GREEN</span></h5>
<div class="source-file">test/models/micropost_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">MicropostTest</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="n">users</span><span class="p">(</span><span class="ss">:michael</span><span class="p">)</span>
<span class="hll"> <span class="vi">@micropost</span> <span class="o">=</span> <span class="vi">@user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">build</span><span class="p">(</span><span class="ss">content</span><span class="p">:</span> <span class="s2">"Lorem ipsum"</span><span class="p">)</span>
</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">@micropost</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="nb">test</span> <span class="s2">"user id should be present"</span> <span class="k">do</span>
<span class="vi">@micropost</span><span class="o">.</span><span class="n">user_id</span> <span class="o">=</span> <span class="kp">nil</span>
<span class="n">assert_not</span> <span class="vi">@micropost</span><span class="o">.</span><span class="n">valid?</span>
<span class="k">end</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="k">end</span>
</pre></div>
</div>
<p>当然，经过这次简单的重构后测试组件应该还能通过：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 11.12</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="micropost-refinements">
<h2><span class="title-label">11.1.4</span> 改进微博模型</h2>
<p>本节，我们要改进一下用户和微博之间的关联：按照特定的顺序取回用户的微博，并且让微博依属于用户，如果用户注销了，就自动删除这个用户发布的所有微博。</p>
<section data-type="sect3" id="default-scope">
<h3>默认作用域</h3>
<p>默认情况下，<code>user.microposts</code> 不能确保微博的顺序，但是按照博客和 Twitter 的习惯，我们希望微博按照创建时间倒序排列，也就是最新发布的微博在前面。<sup>[<a id="fn-ref-1" href="#fn-1">1</a>]</sup>为此，我们要使用“默认作用域”（default scope）。</p>
<p>这样的功能很容易让测试意外通过（就算应用代码不对，测试也能通过），所以我们要使用测试驱动开发技术，确保实现的方式是正确的。首先，我们编写一个测试，检查数据库中的第一篇微博和微博固件中名为 <code>most_recent</code> 的微博相同，如<a href="#listing-micropost-order-test">代码清单 11.13</a> 所示。</p>
<div id="listing-micropost-order-test" data-type="listing">
<h5><span class="title-label">代码清单 11.13</span>：测试微博的排序 <span class="red">RED</span></h5>
<div class="source-file">test/models/micropost_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">MicropostTest</span> <span class="o"><</span> <span class="no">ActiveSupport</span><span class="o">::</span><span class="no">TestCase</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="nb">test</span> <span class="s2">"order should be most recent first"</span> <span class="k">do</span>
<span class="n">assert_equal</span> <span class="no">Micropost</span><span class="o">.</span><span class="n">first</span><span class="p">,</span> <span class="n">microposts</span><span class="p">(</span><span class="ss">:most_recent</span><span class="p">)</span>
<span class="k">end</span>
<span class="k">end</span>
</pre></div>
</div>
<p>这段代码要使用微博固件，所以我们要定义固件，如<a href="#listing-micropost-fixtures">代码清单 11.14</a> 所示。</p>
<div id="listing-micropost-fixtures" data-type="listing">
<h5><span class="title-label">代码清单 11.14</span>：微博固件</h5>
<div class="source-file">test/fixtures/microposts.yml</div>
<div class="highlight language-yaml"><pre><span class="l-Scalar-Plain">orange</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">content</span><span class="p-Indicator">:</span> <span class="s">"I</span><span class="nv"> </span><span class="s">just</span><span class="nv"> </span><span class="s">ate</span><span class="nv"> </span><span class="s">an</span><span class="nv"> </span><span class="s">orange!"</span>
<span class="l-Scalar-Plain">created_at</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= 10.minutes.ago %></span>
<span class="l-Scalar-Plain">tau_manifesto</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">content</span><span class="p-Indicator">:</span> <span class="s">"Check</span><span class="nv"> </span><span class="s">out</span><span class="nv"> </span><span class="s">the</span><span class="nv"> </span><span class="s">@tauday</span><span class="nv"> </span><span class="s">site</span><span class="nv"> </span><span class="s">by</span><span class="nv"> </span><span class="s">@mhartl:</span><span class="nv"> </span><span class="s">http://tauday.com"</span>
<span class="l-Scalar-Plain">created_at</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= 3.years.ago %></span>
<span class="l-Scalar-Plain">cat_video</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">content</span><span class="p-Indicator">:</span> <span class="s">"Sad</span><span class="nv"> </span><span class="s">cats</span><span class="nv"> </span><span class="s">are</span><span class="nv"> </span><span class="s">sad:</span><span class="nv"> </span><span class="s">http://youtu.be/PKffm2uI4dk"</span>
<span class="l-Scalar-Plain">created_at</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= 2.hours.ago %></span>
<span class="l-Scalar-Plain">most_recent</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">content</span><span class="p-Indicator">:</span> <span class="s">"Writing</span><span class="nv"> </span><span class="s">a</span><span class="nv"> </span><span class="s">short</span><span class="nv"> </span><span class="s">test"</span>
<span class="l-Scalar-Plain">created_at</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= Time.zone.now %></span>
</pre></div>
</div>
<p>注意，我们使用嵌入式 Ruby 明确设置了 <code>created_at</code> 属性的值。因为这个属性由 Rails 自动更新，一般无法手动设置，但在固件中可以这么做。实际上可能不用自己设置这些属性，因为在某些系统中固件会按照定义的顺序创建。在这个文件中，最后一个固件最后创建（因此是最新的一篇微博）。但是绝不要依赖这种行为，因为并不可靠，而且在不同的系统中有差异。</p>
<p>现在，测试应该无法通过：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 11.15</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><span class="nv">TEST</span><span class="o">=</span><span class="nb">test</span>/models/micropost_test.rb <span class="se">\</span>
> <span class="nv">TESTOPTS</span><span class="o">=</span><span class="s2">"--name test_order_should_be_most_recent_first"</span>
</pre></div>
</div>
<p>我们要使用 Rails 提供的 <code>default_scope</code> 方法让测试通过。这个方法的作用很多，这里我们要用它设定从数据库中读取数据的默认顺序。为了得到特定的顺序，我们要在 <code>default_scope</code> 方法中指定 <code>order</code> 参数，按 <code>created_at</code> 列的值排序，如下所示：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="n">order</span><span class="p">(</span><span class="ss">:created_at</span><span class="p">)</span>
</pre></div>
</div>
<p>可是，这实现的是“升序”，从小到大排列，即最早发布的微博排在最前面。为了让微博降序排列，我们要向下走一层，使用纯 SQL 语句：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="n">order</span><span class="p">(</span><span class="s1">'created_at DESC'</span><span class="p">)</span>
</pre></div>
</div>
<p>在 SQL 中，<code>DESC</code> 表示“降序”，即新发布的微博在前面。在以前的 Rails 版本中，必须使用纯 SQL 语句才能实现这个需求，但从 Rails 4.0 起，可以使用纯 Ruby 句法实现：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="n">order</span><span class="p">(</span><span class="ss">created_at</span><span class="p">:</span> <span class="ss">:desc</span><span class="p">)</span>
</pre></div>
</div>
<p>把默认作用域加入微博模型，如<a href="#listing-micropost-ordering">代码清单 11.16</a> 所示。</p>
<div id="listing-micropost-ordering" data-type="listing">
<h5><span class="title-label">代码清单 11.16</span>：使用 <code>default_scope</code> 排序微博 <span class="green">GREEN</span></h5>
<div class="source-file">app/models/micropost.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">Micropost</span> <span class="o"><</span> <span class="no">ActiveRecord</span><span class="o">::</span><span class="no">Base</span>
<span class="n">belongs_to</span> <span class="ss">:user</span>
<span class="hll"> <span class="n">default_scope</span> <span class="o">-></span> <span class="p">{</span> <span class="n">order</span><span class="p">(</span><span class="ss">created_at</span><span class="p">:</span> <span class="ss">:desc</span><span class="p">)</span> <span class="p">}</span>
</span> <span class="n">validates</span> <span class="ss">:user_id</span><span class="p">,</span> <span class="ss">presence</span><span class="p">:</span> <span class="kp">true</span>
<span class="n">validates</span> <span class="ss">:content</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">140</span> <span class="p">}</span>
<span class="k">end</span>
</pre></div>
</div>
<p><a href="#listing-micropost-ordering">代码清单 11.16</a> 中使用了“箭头”句法，表示一种对象，叫 Proc（procedure）或 lambda，即“匿名函数”（没有名字的函数）。<code>-></code> 接受一个代码块（<a href="chapter4.html#blocks">4.3.2 节</a>），返回一个 Proc。然后在这个 Proc 上调用 <code>call</code> 方法执行其中的代码。我们可以在控制台中看一下怎么使用 Proc：</p>
<div data-type="listing">
<div class="highlight language-irb"><pre><span class="gp">>> </span><span class="o">-></span> <span class="p">{</span> <span class="nb">puts</span> <span class="s2">"foo"</span> <span class="p">}</span>
<span class="go">=> #<Proc:0x007fab938d0108@(irb):1 (lambda)></span>
<span class="gp">>> </span><span class="o">-></span> <span class="p">{</span> <span class="nb">puts</span> <span class="s2">"foo"</span> <span class="p">}</span><span class="o">.</span><span class="n">call</span>
<span class="go">foo</span>
<span class="go">=> nil</span>
</pre></div>
</div>
<p>（Proc 是高级 Ruby 知识，如果现在不理解也不用担心。）</p>
<p>按照<a href="#listing-micropost-ordering">代码清单 11.16</a> 修改后，测试应该可以通过了：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 11.17</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>
</section>
<section data-type="sect3" id="dependent-destroy">
<h3>依属关系：destroy</h3>
<p>除了设定恰当的顺序外，我们还要对微博模型做一项改进。我们在 <a href="chapter9.html#deleting-users">9.4 节</a>介绍过，管理员有删除用户的权限。那么，在删除用户的同时，有必要把该用户发布的微博也删除。</p>
<p>为此，我们可以把一个参数传给 <code>has_many</code> 关联方法，如<a href="#listing-micropost-dependency">代码清单 11.18</a> 所示。</p>
<div id="listing-micropost-dependency" data-type="listing">
<h5><span class="title-label">代码清单 11.18</span>：确保用户的微博在删除用户的同时也被删除</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">has_many</span> <span class="ss">:microposts</span><span class="p">,</span> <span class="ss">dependent</span><span class="p">:</span> <span class="ss">:destroy</span>
</span> <span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="k">end</span>
</pre></div>
</div>
<p><code>dependent: :destroy</code> 的作用是在用户被删除的时候，把这个用户发布的微博也删除。这么一来，如果管理员删除了用户，数据库中就不会出现无主的微博了。</p>
<p>我们可以为用户模型编写一个测试，证明<a href="#listing-micropost-dependency">代码清单 11.18</a> 中的代码是正确的。我们要保存一个用户（因此得到了用户的 ID），再创建一个属于这个用户的微博，然后检查删除用户后微博的数量有没有减少一个，如<a href="#listing-dependent-destroy-test">代码清单 11.19</a> 所示。（和<a href="chapter9.html#listing-delete-link-integration-test">代码清单 9.57</a> 中“删除”链接的集成测试对比一下。）</p>
<div id="listing-dependent-destroy-test" data-type="listing">
<h5><span class="title-label">代码清单 11.19</span>：测试 <code>dependent: :destroy</code> <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">"user@example.com"</span><span class="p">,</span>
<span class="ss">password</span><span class="p">:</span> <span class="s2">"foobar"</span><span class="p">,</span> <span class="ss">password_confirmation</span><span class="p">:</span> <span class="s2">"foobar"</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">"associated microposts should be destroyed"</span> <span class="k">do</span>
<span class="vi">@user</span><span class="o">.</span><span class="n">save</span>
<span class="vi">@user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">create!</span><span class="p">(</span><span class="ss">content</span><span class="p">:</span> <span class="s2">"Lorem ipsum"</span><span class="p">)</span>
<span class="n">assert_difference</span> <span class="s1">'Micropost.count'</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span> <span class="k">do</span>
<span class="vi">@user</span><span class="o">.</span><span class="n">destroy</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">end</span>
</pre></div>
</div>
<p>如果<a href="#listing-micropost-dependency">代码清单 11.18</a> 正确，测试组件就应该能通过：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 11.20</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>
</section>
<section data-type="sect1" id="showing-microposts">
<h1><span class="title-label">11.2</span> 显示微博</h1>
<p>尽管我们还没实现直接在网页中发布微博的功能（将在 <a href="#creating-microposts">11.3.2 节</a>实现），不过还是有办法显示微博，并对显示的内容进行测试。我们将按照 Twitter 的方式，不在微博资源的 <code>index</code> 页面显示用户的微博，而在用户资源的 <code>show</code> 页面显示，构思图如<a href="#fig-user-microposts-mockup">图 11.4</a> 所示。我们会先使用一些简单的 ERb 代码，在用户的资料页面显示微博，然后在 <a href="chapter9.html#sample-users">9.3.2 节</a>的种子数据中添加一些微博，这样才有内容可以显示。</p>
<div id="fig-user-microposts-mockup" class="figure"><img src="images/chapter11/user_microposts_mockup_3rd_edition.png" alt="user microposts mockup 3rd edition" /><div class="figcaption"><span class="title-label">图 11.4</span>：显示有微博的资料页面构思图</div></div>
<section data-type="sect2" id="rendering-microposts">
<h2><span class="title-label">11.2.1</span> 渲染微博</h2>
<p>我们计划在用户的资料页面（<code>show.html.erb</code>）显示用户的微博，还要显示用户发布了多少篇微博。你会发现，很多做法和 <a href="chapter9.html#showing-all-users">9.3 节</a>列出所有用户时类似。</p>
<p>虽然 <a href="#manipulating-microposts">11.3 节</a>才会用到微博控制器，但马上就需要使用视图，所以现在就要生成控制器：</p>
<div data-type="listing">
<div class="highlight language-sh"><pre><span class="nv">$ </span>rails generate controller Microposts
</pre></div>
</div>
<p>这一节的主要目的是渲染用户发布的所有微博。<a href="chapter9.html#partial-refactoring">9.3.5 节</a>用过这样的代码：</p>
<div data-type="listing">
<div class="highlight language-erb"><pre><span class="x"><ul class="users"></span>
<span class="x"> </span><span class="cp"><%=</span> <span class="n">render</span> <span class="vi">@users</span> <span class="cp">%></span><span class="x"></span>
<span class="x"></ul></span>
</pre></div>
</div>
<p>这段代码会自动使用局部视图 <code>_user.html.erb</code> 渲染 <code>@users</code> 变量中的每个用户。同样地，我们要编写 <code>_micropost.html.erb</code> 局部视图，使用类似的方式渲染微博集合：</p>
<div data-type="listing">
<div class="highlight language-erb"><pre><span class="x"><ol class="microposts"></span>
<span class="x"> </span><span class="cp"><%=</span> <span class="n">render</span> <span class="vi">@microposts</span> <span class="cp">%></span><span class="x"></span>
<span class="x"></ol></span>
</pre></div>
</div>
<p>注意，我们使用的是有序列表标签 <code>ol</code>（而不是无需列表 <code>ul</code>），因为微博是按照一定顺序显示的（按时间倒序）。相应的局部视图如<a href="#listing-micropost-partial">代码清单 11.21</a> 所示。</p>
<div id="listing-micropost-partial" data-type="listing">
<h5><span class="title-label">代码清单 11.21</span>：渲染单篇微博的局部视图</h5>
<div class="source-file">app/views/microposts/_micropost.html.erb</div>
<div class="highlight language-erb"><pre><span class="x"><li id="micropost-</span><span class="cp"><%=</span> <span class="n">micropost</span><span class="o">.</span><span class="n">id</span> <span class="cp">%></span><span class="x">"></span>
<span class="x"> </span><span class="cp"><%=</span> <span class="n">link_to</span> <span class="n">gravatar_for</span><span class="p">(</span><span class="n">micropost</span><span class="o">.</span><span class="n">user</span><span class="p">,</span> <span class="ss">size</span><span class="p">:</span> <span class="mi">50</span><span class="p">),</span> <span class="n">micropost</span><span class="o">.</span><span class="n">user</span> <span class="cp">%></span><span class="x"></span>
<span class="x"> <span class="user"></span><span class="cp"><%=</span> <span class="n">link_to</span> <span class="n">micropost</span><span class="o">.</span><span class="n">user</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="n">micropost</span><span class="o">.</span><span class="n">user</span> <span class="cp">%></span><span class="x"></span></span>
<span class="x"> <span class="content"></span><span class="cp"><%=</span> <span class="n">micropost</span><span class="o">.</span><span class="n">content</span> <span class="cp">%></span><span class="x"></span></span>
<span class="x"> <span class="timestamp"></span>
<span class="x"> Posted </span><span class="cp"><%=</span> <span class="n">time_ago_in_words</span><span class="p">(</span><span class="n">micropost</span><span class="o">.</span><span class="n">created_at</span><span class="p">)</span> <span class="cp">%></span><span class="x"> ago.</span>
<span class="x"> </span></span>
<span class="x"></li></span>
</pre></div>
</div>
<p>这个局部视图使用了 <code>time_ago_in_words</code> 辅助方法，这个方法的作用应该很明显，效果会在 <a href="#sample-microposts">11.2.2 节</a>看到。<a href="#listing-micropost-partial">代码清单 11.21</a> 还为每篇微博指定了 CSS ID：</p>
<div data-type="listing">
<div class="highlight language-erb"><pre><span class="x"><li id="micropost-</span><span class="cp"><%=</span> <span class="n">micropost</span><span class="o">.</span><span class="n">id</span> <span class="cp">%></span><span class="x">"></span>
</pre></div>
</div>
<p>这是好习惯，说不定以后要处理（例如使用 JavaScript）单篇微博呢。</p>
<p>接下来要解决显示大量微博的问题。我们可以使用 <a href="chapter9.html#pagination">9.3.3 节</a>显示大量用户的方法来解决这个问题，即使用分页。和前面一样，我们要使用 <code>will_paginate</code> 方法：</p>
<div data-type="listing">
<div class="highlight language-erb"><pre><span class="cp"><%=</span> <span class="n">will_paginate</span> <span class="vi">@microposts</span> <span class="cp">%></span><span class="x"></span>
</pre></div>
</div>
<p>如果和用户列表页面的代码（<a href="chapter9.html#listing-will-paginate-index-view">代码清单 9.41</a>）比较的话，会发现之前使用的代码是：</p>
<div data-type="listing">
<div class="highlight language-erb"><pre><span class="cp"><%=</span> <span class="n">will_paginate</span> <span class="cp">%></span><span class="x"></span>
</pre></div>
</div>
<p>前面之所以可以直接调用，是因为在用户控制器中，<code>will_paginate</code> 假定有一个名为 <code>@users</code> 的实例变量（<a href="chapter9.html#pagination">9.3.3 节</a>说过，这个变量所属的类应该是 <code>AvtiveRecord::Relation</code>）。现在，因为还在用户控制器中，但是我们要分页显示微博，所以必须明确地把 <code>@microposts</code> 变量传给 <code>will_paginate</code> 方法。当然了，我们还要在 <code>show</code> 动作中定义 <code>@microposts</code> 变量，如<a href="#listing-user-show-microposts-instance">代码清单 11.22</a> 所示。</p>
<div id="listing-user-show-microposts-instance" data-type="listing">
<h5><span class="title-label">代码清单 11.22</span>：在用户控制器的 <code>show</code> 动作中定义 <code>@microposts</code> 变量</h5>
<div class="source-file">app/controllers/users_controller.rb</div>
<div class="highlight language-ruby"><pre><span class="k">class</span> <span class="nc">UsersController</span> <span class="o"><</span> <span class="no">ApplicationController</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="k">def</span> <span class="nf">show</span>
<span class="vi">@user</span> <span class="o">=</span> <span class="no">User</span><span class="o">.</span><span class="n">find</span><span class="p">(</span><span class="n">params</span><span class="o">[</span><span class="ss">:id</span><span class="o">]</span><span class="p">)</span>
<span class="hll"> <span class="vi">@microposts</span> <span class="o">=</span> <span class="vi">@user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">paginate</span><span class="p">(</span><span class="ss">page</span><span class="p">:</span> <span class="n">params</span><span class="o">[</span><span class="ss">:page</span><span class="o">]</span><span class="p">)</span>
</span> <span class="k">end</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="o">.</span>
<span class="k">end</span>
</pre></div>
</div>
<p>注意看 <code>paginate</code> 方法是多么智能，甚至可以在关联上使用，从 <code>microposts</code> 表中取出每一页要显示的微博。</p>
<p>最后，还要显示用户发布的微博数量。我们可以使用 <code>count</code> 方法实现：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="n">user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">count</span>
</pre></div>
</div>
<p>和 <code>paginate</code> 方法一样，<code>count</code> 方法也可以在关联上使用。<code>count</code> 的计数过程不是把所有微博都从数据库中读取出来，然后再在所得的数组上调用 <code>length</code> 方法，如果这样做的话，微博数量一旦很多，效率就会降低。其实，<code>count</code> 方法直接在数据库层计算，让数据库统计指定的 <code>user_id</code> 拥有多少微博。（所有数据库都会对这种操作做性能优化。如果统计数量仍然是应用的性能瓶颈，可以使用“<a href="http://railscasts.com/episodes/23-counter-cache-column">计数缓存</a>”进一步提速。）</p>
<p>综上所述，现在可以把微博添加到资料页面了，如<a href="#listing-user-show-microposts">代码清单 11.23</a> 所示。注意，<code>if @user.microposts.any?</code>（在<a href="chapter7.html#listing-errors-partial">代码清单 7.19</a> 中见过类似的用法）的作用是，如果用户没有发布微博，不显示一个空列表。</p>
<div id="listing-user-show-microposts" data-type="listing">
<h5><span class="title-label">代码清单 11.23</span>：在用户资料页面中加入微博</h5>
<div class="source-file">app/views/users/show.html.erb</div>
<div class="highlight language-erb"><pre><span class="cp"><%</span> <span class="n">provide</span><span class="p">(</span><span class="ss">:title</span><span class="p">,</span> <span class="vi">@user</span><span class="o">.</span><span class="n">name</span><span class="p">)</span> <span class="cp">%></span><span class="x"></span>
<span class="x"><div class="row"></span>
<span class="x"> <aside class="col-md-4"></span>
<span class="x"> <section class="user_info"></span>
<span class="x"> <h1></span>
<span class="x"> </span><span class="cp"><%=</span> <span class="n">gravatar_for</span> <span class="vi">@user</span> <span class="cp">%></span><span class="x"></span>
<span class="x"> </span><span class="cp"><%=</span> <span class="vi">@user</span><span class="o">.</span><span class="n">name</span> <span class="cp">%></span><span class="x"></span>
<span class="x"> </h1></span>
<span class="x"> </section></span>
<span class="x"> </aside></span>
<span class="hll"><span class="x"> <div class="col-md-8"></span>
</span><span class="hll"><span class="x"> </span><span class="cp"><%</span> <span class="k">if</span> <span class="vi">@user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">any?</span> <span class="cp">%></span><span class="x"></span>
</span><span class="hll"><span class="x"> <h3>Microposts (</span><span class="cp"><%=</span> <span class="vi">@user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">count</span> <span class="cp">%></span><span class="x">)</h3></span>
</span><span class="hll"><span class="x"> <ol class="microposts"></span>
</span><span class="hll"><span class="x"> </span><span class="cp"><%=</span> <span class="n">render</span> <span class="vi">@microposts</span> <span class="cp">%></span><span class="x"></span>
</span><span class="hll"><span class="x"> </ol></span>
</span><span class="hll"><span class="x"> </span><span class="cp"><%=</span> <span class="n">will_paginate</span> <span class="vi">@microposts</span> <span class="cp">%></span><span class="x"></span>
</span><span class="hll"><span class="x"> </span><span class="cp"><%</span> <span class="k">end</span> <span class="cp">%></span><span class="x"></span>
</span><span class="hll"><span class="x"> </div></span>
</span><span class="x"></div></span>
</pre></div>
</div>
<p>现在，我们可以查看一下修改后的用户资料页面，如<a href="#fig-user-profile-no-microposts">图 11.5</a>。可能会出乎你的意料，不过也是理所当然的，因为现在还没有微博。下面我们就来改变这种状况。</p>
<div id="fig-user-profile-no-microposts" class="figure"><img src="images/chapter11/user_profile_no_microposts_3rd_edition.png" alt="user profile no microposts 3rd edition" /><div class="figcaption"><span class="title-label">图 11.5</span>：添加显示微博的代码后用户的资料页面，但没有微博</div></div>
</section>
<section data-type="sect2" id="sample-microposts">
<h2><span class="title-label">11.2.2</span> 示例微博</h2>
<p>在 <a href="#rendering-microposts">11.2.1 节</a>，为了显示用户的微博，创建或修改了几个模板，但是结果有点不给力。为了改变这种状况，我们要在 <a href="chapter9.html#sample-users">9.3.2 节</a>用到的种子数据中加入一些微博。</p>
<p>为所有用户添加示例微博要花很长时间，所以我们决定只为前六个用户添加。为此，要使用 <code>take</code> 方法：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="no">User</span><span class="o">.</span><span class="n">order</span><span class="p">(</span><span class="ss">:created_at</span><span class="p">)</span><span class="o">.</span><span class="n">take</span><span class="p">(</span><span class="mi">6</span><span class="p">)</span>
</pre></div>
</div>
<p>调用 <code>order</code> 方法的作用是按照创建用户的顺序查找六个用户。</p>
<p>我们要分别为这六个用户创建 50 篇微博（数量要多于 30 个才能分页）。为了生成微博的内容，我们要使用 Faker 提供的 <a href="http://rubydoc.info/gems/faker/1.3.0/Faker/Lorem"><code>Lorem.sentence</code></a> 方法。<sup>[<a id="fn-ref-2" href="#fn-2">2</a>]</sup>添加示例微博后的种子数据如<a href="#listing-sample-microposts">代码清单 11.24</a> 所示。</p>
<div id="listing-sample-microposts" data-type="listing">
<h5><span class="title-label">代码清单 11.24</span>：添加示例微博</h5>
<div class="source-file">db/seeds.rb</div>
<div class="highlight language-yaml"><pre><span class="l-Scalar-Plain">.</span>
<span class="l-Scalar-Plain">.</span>
<span class="l-Scalar-Plain">.</span>
<span class="l-Scalar-Plain">users = User.order(:created_at).take(6)</span>
<span class="l-Scalar-Plain">50.times do</span>
<span class="l-Scalar-Plain">content = Faker::Lorem.sentence(5)</span>
<span class="l-Scalar-Plain">users.each { |user| user.microposts.create!(content</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">content) }</span>
<span class="l-Scalar-Plain">end</span>
</pre></div>
</div>
<p>然后，像之前一样重新把种子数据写入开发数据库：</p>
<div data-type="listing">
<div class="highlight language-sh"><pre><span class="nv">$ </span>bundle <span class="nb">exec </span>rake db:migrate:reset
<span class="nv">$ </span>bundle <span class="nb">exec </span>rake db:seed
</pre></div>
</div>
<p>完成后还要重启 Rails 开发服务器。</p>
<p>现在，我们能看到 <a href="#rendering-microposts">11.2.1 节</a>的劳动成果了——用户资料页面显示了微博。<sup>[<a id="fn-ref-3" href="#fn-3">3</a>]</sup>初步结果如<a href="#fig-user-profile-microposts-no-styling">图 11.6</a> 所示。</p>
<div id="fig-user-profile-microposts-no-styling" class="figure"><img src="images/chapter11/user_profile_microposts_no_styling_3rd_edition.png" alt="user profile microposts no styling 3rd edition" /><div class="figcaption"><span class="title-label">图 11.6</span>：用户资料页面显示的微博，还没添加样式</div></div>
<p><a href="#fig-user-profile-microposts-no-styling">图 11.6</a> 中显示的微博还没有样式，那我们就加入一些样式，如<a href="#listing-micropost-css">代码清单 11.25</a> 所示，<sup>[<a id="fn-ref-4" href="#fn-4">4</a>]</sup>然后再看一下页面显示的效果。</p>
<div id="listing-micropost-css" data-type="listing">
<h5><span class="title-label">代码清单 11.25</span>：微博的样式（包含本章要使用的所有 CSS）</h5>
<div class="source-file">app/assets/stylesheets/custom.css.scss</div>
<div class="highlight language-scss"><pre><span class="nc">.</span>
<span class="nc">.</span>
<span class="nc">.</span>
<span class="o">/*</span> <span class="nt">microposts</span> <span class="o">*/</span>
<span class="nc">.microposts</span> <span class="p">{</span>
<span class="na">list-style</span><span class="o">:</span> <span class="no">none</span><span class="p">;</span>
<span class="na">padding</span><span class="o">:</span> <span class="mi">0</span><span class="p">;</span>
<span class="nt">li</span> <span class="p">{</span>
<span class="na">padding</span><span class="o">:</span> <span class="mi">10</span><span class="kt">px</span> <span class="mi">0</span><span class="p">;</span>
<span class="na">border-top</span><span class="o">:</span> <span class="mi">1</span><span class="kt">px</span> <span class="no">solid</span> <span class="mh">#e8e8e8</span><span class="p">;</span>
<span class="p">}</span>
<span class="nc">.user</span> <span class="p">{</span>
<span class="na">margin-top</span><span class="o">:</span> <span class="mi">5</span><span class="kt">em</span><span class="p">;</span>
<span class="na">padding-top</span><span class="o">:</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
<span class="nc">.content</span> <span class="p">{</span>
<span class="na">display</span><span class="o">:</span> <span class="no">block</span><span class="p">;</span>
<span class="na">margin-left</span><span class="o">:</span> <span class="mi">60</span><span class="kt">px</span><span class="p">;</span>
<span class="nt">img</span> <span class="p">{</span>
<span class="na">display</span><span class="o">:</span> <span class="no">block</span><span class="p">;</span>
<span class="na">padding</span><span class="o">:</span> <span class="mi">5</span><span class="kt">px</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="nc">.timestamp</span> <span class="p">{</span>
<span class="na">color</span><span class="o">:</span> <span class="nv">$gray-light</span><span class="p">;</span>
<span class="na">display</span><span class="o">:</span> <span class="no">block</span><span class="p">;</span>
<span class="na">margin-left</span><span class="o">:</span> <span class="mi">60</span><span class="kt">px</span><span class="p">;</span>
<span class="p">}</span>
<span class="nc">.gravatar</span> <span class="p">{</span>
<span class="na">float</span><span class="o">:</span> <span class="no">left</span><span class="p">;</span>
<span class="na">margin-right</span><span class="o">:</span> <span class="mi">10</span><span class="kt">px</span><span class="p">;</span>
<span class="na">margin-top</span><span class="o">:</span> <span class="mi">5</span><span class="kt">px</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="nt">aside</span> <span class="p">{</span>
<span class="nt">textarea</span> <span class="p">{</span>
<span class="na">height</span><span class="o">:</span> <span class="mi">100</span><span class="kt">px</span><span class="p">;</span>
<span class="na">margin-bottom</span><span class="o">:</span> <span class="mi">5</span><span class="kt">px</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="nt">span</span><span class="nc">.picture</span> <span class="p">{</span>
<span class="na">margin-top</span><span class="o">:</span> <span class="mi">10</span><span class="kt">px</span><span class="p">;</span>
<span class="nt">input</span> <span class="p">{</span>
<span class="na">border</span><span class="o">:</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
<p><a href="#fig-user-profile-with-microposts">图 11.7</a> 是第一个用户的资料页面，<a href="#fig-other-profile-with-microposts">图 11.8</a> 是另一个用户的资料页面，<a href="#fig-user-profile-microposts">图 11.9</a> 是第一个用户资料页面的第 2 页，页面底部还显示了分页链接。注意观察这三幅图，可以看到，微博后面显示了距离发布的时间（例如，“Posted 1 minute ago.”），这就是<a href="#listing-micropost-partial">代码清单 11.21</a> 中 <code>time_ago_in_words</code> 方法实现的效果。过一会再刷新页面，这些文字会根据当前时间自动更新。</p>
<div id="fig-user-profile-with-microposts" class="figure"><img src="images/chapter11/user_profile_with_microposts_3rd_edition.png" alt="user profile with microposts 3rd edition" /><div class="figcaption"><span class="title-label">图 11.7</span>：显示有微博的用户资料页面（<a href="http://localhost:3000/users/1">/users/1</a>）</div></div>
<div id="fig-other-profile-with-microposts" class="figure"><img src="images/chapter11/other_profile_with_microposts_3rd_edition.png" alt="other profile with microposts 3rd edition" /><div class="figcaption"><span class="title-label">图 11.8</span>：另一个用户的资料页面（<a href="http://localhost:3000/users/5">/users/5</a>），也显示有微博</div></div>
<div id="fig-user-profile-microposts" class="figure"><img src="images/chapter11/user_profile_microposts_page_2_3rd_edition.png" alt="user profile microposts page 2 3rd edition" /><div class="figcaption"><span class="title-label">图 11.9</span>：微博分页链接（<a href="http://localhost:3000/users/1?page=2">/users/1?page=2</a>）</div></div>
</section>
<section data-type="sect2" id="profile-micropost-tests">
<h2><span class="title-label">11.2.3</span> 资料页面中微博的测试</h2>
<p>新激活的用户会重定向到资料页面，那时已经测试了资料页面是否能正确渲染（<a href="chapter10.html#listing-signup-with-account-activation-test">代码清单 10.31</a>）。本节，我们要编写几个简短的集成测试，检查资料页面中的其他内容。首先，生成资料页面的集成测试文件：</p>
<div data-type="listing">
<div class="highlight language-sh"><pre><span class="nv">$ </span>rails generate integration_test users_profile
invoke test_unit
create <span class="nb">test</span>/integration/users_profile_test.rb
</pre></div>
</div>
<p>为了测试资料页面中显示有微博，我们要把微博固件和用户关联起来。Rails 提供了一种便利的方法，可以在固件中建立关联，例如：</p>
<div data-type="listing">
<div class="highlight language-yaml"><pre><span class="l-Scalar-Plain">orange</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">content</span><span class="p-Indicator">:</span> <span class="s">"I</span><span class="nv"> </span><span class="s">just</span><span class="nv"> </span><span class="s">ate</span><span class="nv"> </span><span class="s">an</span><span class="nv"> </span><span class="s">orange!"</span>
<span class="l-Scalar-Plain">created_at</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= 10.minutes.ago %></span>
<span class="hll"> <span class="l-Scalar-Plain">user</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">michael</span>
</span></pre></div>
</div>
<p>把 <code>user</code> 的值设为 <code>michael</code> 后，Rails 会把这篇微博和指定的用户固件关联起来：</p>
<div data-type="listing">
<div class="highlight language-yaml"><pre><span class="hll"><span class="l-Scalar-Plain">michael</span><span class="p-Indicator">:</span>
</span> <span class="l-Scalar-Plain">name</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">Michael Example</span>
<span class="l-Scalar-Plain">email</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">michael@example.com</span>
<span class="l-Scalar-Plain">.</span>
<span class="l-Scalar-Plain">.</span>
<span class="l-Scalar-Plain">.</span>
</pre></div>
</div>
<p>为了测试微博分页，我们要使用<a href="chapter9.html#listing-users-fixtures-extra-users">代码清单 9.43</a> 中用到的方法，通过嵌入式 Ruby 代码多生成一些微博固件：</p>
<div data-type="listing">
<div class="highlight language-yaml"><pre><span class="l-Scalar-Plain"><% 30.times do |n| %></span>
<span class="l-Scalar-Plain">micropost_<%= n %></span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">content</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= Faker::Lorem.sentence(5) %></span>
<span class="l-Scalar-Plain">created_at</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= 42.days.ago %></span>
<span class="l-Scalar-Plain">user</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">michael</span>
<span class="l-Scalar-Plain"><% end %></span>
</pre></div>
</div>
<p>综上，修改后的微博固件如<a href="#listing-updated-micropost-fixtures">代码清单 11.26</a> 所示。</p>
<div id="listing-updated-micropost-fixtures" data-type="listing">
<h5><span class="title-label">代码清单 11.26</span>：添加关联用户后的微博固件</h5>
<div class="source-file">test/fixtures/microposts.yml</div>
<div class="highlight language-yaml"><pre><span class="l-Scalar-Plain">orange</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">content</span><span class="p-Indicator">:</span> <span class="s">"I</span><span class="nv"> </span><span class="s">just</span><span class="nv"> </span><span class="s">ate</span><span class="nv"> </span><span class="s">an</span><span class="nv"> </span><span class="s">orange!"</span>
<span class="l-Scalar-Plain">created_at</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= 10.minutes.ago %></span>
<span class="hll"> <span class="l-Scalar-Plain">user</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">michael</span>
</span>
<span class="l-Scalar-Plain">tau_manifesto</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">content</span><span class="p-Indicator">:</span> <span class="s">"Check</span><span class="nv"> </span><span class="s">out</span><span class="nv"> </span><span class="s">the</span><span class="nv"> </span><span class="s">@tauday</span><span class="nv"> </span><span class="s">site</span><span class="nv"> </span><span class="s">by</span><span class="nv"> </span><span class="s">@mhartl:</span><span class="nv"> </span><span class="s">http://tauday.com"</span>
<span class="l-Scalar-Plain">created_at</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= 3.years.ago %></span>
<span class="hll"> <span class="l-Scalar-Plain">user</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">michael</span>
</span>
<span class="l-Scalar-Plain">cat_video</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">content</span><span class="p-Indicator">:</span> <span class="s">"Sad</span><span class="nv"> </span><span class="s">cats</span><span class="nv"> </span><span class="s">are</span><span class="nv"> </span><span class="s">sad:</span><span class="nv"> </span><span class="s">http://youtu.be/PKffm2uI4dk"</span>
<span class="l-Scalar-Plain">created_at</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= 2.hours.ago %></span>
<span class="hll"> <span class="l-Scalar-Plain">user</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">michael</span>
</span>
<span class="l-Scalar-Plain">most_recent</span><span class="p-Indicator">:</span>
<span class="l-Scalar-Plain">content</span><span class="p-Indicator">:</span> <span class="s">"Writing</span><span class="nv"> </span><span class="s">a</span><span class="nv"> </span><span class="s">short</span><span class="nv"> </span><span class="s">test"</span>
<span class="l-Scalar-Plain">created_at</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= Time.zone.now %></span>
<span class="hll"> <span class="l-Scalar-Plain">user</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">michael</span>
</span>
<span class="hll"><span class="l-Scalar-Plain"><% 30.times do |n| %></span>
</span><span class="hll"><span class="l-Scalar-Plain">micropost_<%= n %></span><span class="p-Indicator">:</span>
</span><span class="hll"> <span class="l-Scalar-Plain">content</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= Faker::Lorem.sentence(5) %></span>
</span><span class="hll"> <span class="l-Scalar-Plain">created_at</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain"><%= 42.days.ago %></span>
</span><span class="hll"> <span class="l-Scalar-Plain">user</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">michael</span>
</span><span class="hll"><span class="l-Scalar-Plain"><% end %></span>
</span></pre></div>
</div>
<p>测试数据准备好了，测试本身也很简单：访问资料页面，检查页面的标题、用户的名字、Gravatar 头像、微博数量和分页显示的微博，如<a href="#listing-user-profile-test">代码清单 11.27</a> 所示。注意，为了使用<a href="chapter4.html#listing-title-helper">代码清单 4.2</a> 中的 <code>full_title</code> 辅助方法测试页面的标题，我们要把 <code>ApplicationHelper</code> 模块引入测试。<sup>[<a id="fn-ref-5" href="#fn-5">5</a>]</sup></p>
<div id="listing-user-profile-test" data-type="listing">
<h5><span class="title-label">代码清单 11.27</span>：用户资料页面的测试 <span class="green">GREEN</span></h5>
<div class="source-file">test/integration/users_profile_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">UsersProfileTest</span> <span class="o"><</span> <span class="no">ActionDispatch</span><span class="o">::</span><span class="no">IntegrationTest</span>
<span class="hll"> <span class="kp">include</span> <span class="no">ApplicationHelper</span>
</span>
<span class="k">def</span> <span class="nf">setup</span>
<span class="vi">@user</span> <span class="o">=</span> <span class="n">users</span><span class="p">(</span><span class="ss">:michael</span><span class="p">)</span>
<span class="k">end</span>
<span class="nb">test</span> <span class="s2">"profile display"</span> <span class="k">do</span>
<span class="n">get</span> <span class="n">user_path</span><span class="p">(</span><span class="vi">@user</span><span class="p">)</span>
<span class="n">assert_template</span> <span class="s1">'users/show'</span>
<span class="n">assert_select</span> <span class="s1">'title'</span><span class="p">,</span> <span class="n">full_title</span><span class="p">(</span><span class="vi">@user</span><span class="o">.</span><span class="n">name</span><span class="p">)</span>
<span class="n">assert_select</span> <span class="s1">'h1'</span><span class="p">,</span> <span class="ss">text</span><span class="p">:</span> <span class="vi">@user</span><span class="o">.</span><span class="n">name</span>
<span class="n">assert_select</span> <span class="s1">'h1>img.gravatar'</span>
<span class="n">assert_match</span> <span class="vi">@user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">count</span><span class="o">.</span><span class="n">to_s</span><span class="p">,</span> <span class="n">response</span><span class="o">.</span><span class="n">body</span>
<span class="n">assert_select</span> <span class="s1">'div.pagination'</span>
<span class="vi">@user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">paginate</span><span class="p">(</span><span class="ss">page</span><span class="p">:</span> <span class="mi">1</span><span class="p">)</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">micropost</span><span class="o">|</span>
<span class="n">assert_match</span> <span class="n">micropost</span><span class="o">.</span><span class="n">content</span><span class="p">,</span> <span class="n">response</span><span class="o">.</span><span class="n">body</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">end</span>
</pre></div>
</div>
<p>检查微博数量时用到了 <code>response.body</code>，<a href="chapter10.html#account-activation-and-password-reset-exercises">第 10 章的练习</a>中见过。别被名字迷惑了，其实 <code>response.body</code> 的值是整个页面的 HTML 源码（不只是 <code>body</code> 元素中的内容）。如果我们只关心页面中某处显示的微博数量，使用下面的断言找到匹配的内容即可：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="n">assert_match</span> <span class="vi">@user</span><span class="o">.</span><span class="n">microposts</span><span class="o">.</span><span class="n">count</span><span class="o">.</span><span class="n">to_s</span><span class="p">,</span> <span class="n">response</span><span class="o">.</span><span class="n">body</span>
</pre></div>
</div>
<p><code>assert_match</code> 没有 <code>assert_select</code> 的针对性强，无需指定要查找哪个 HTML 标签。</p>
<p><a href="#listing-user-profile-test">代码清单 11.27</a> 还在 <code>assert_select</code> 中使用了嵌套式句法：</p>
<div data-type="listing">
<div class="highlight language-ruby"><pre><span class="n">assert_select</span> <span class="s1">'h1>img.gravatar'</span>
</pre></div>
</div>
<p>这行代码的意思是，在 <code>h1</code> 标签中查找类为 <code>gravatar</code> 的 <code>img</code> 标签。</p>
<p>因为应用能正常运行，所以测试组件应该也能通过：</p>
<div data-type="listing">
<h5><span class="title-label">代码清单 11.28</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>
<section data-type="sect1" id="manipulating-microposts">
<h1><span class="title-label">11.3</span> 微博相关的操作</h1>
<p>微博的数据模型构建好了，也编写了相关的视图文件，接下来我们的开发重点是，通过网页发布微博。本节，我们会初步实现动态流，<a href="chapter12.html#following-users">第 12 章</a>再完善。最后，和用户资源一样，我们还要实现在网页中删除微博的功能。</p>
<p>上述功能的实现和之前的方式有点不同，需要特别注意：微博资源相关的页面不通过微博控制器实现，而是通过资料页面和首页实现。因此微博控制器不需要 <code>new</code> 和 <code>edit</code> 动作，只需要 <code>create</code> 和 <code>destroy</code> 动作。所以，微博资源的路由如<a href="#listing-microposts-resource">代码清单 11.29</a> 所示。 <a href="#listing-microposts-resource">代码清单 11.29</a> 中的代码对应的 REST 路由如<a href="#table-restful-microposts">表 11.2</a> 所示，这张表中的路由只是<a href="chapter2.html#table-demo-restful-microposts">表 2.3</a> 的一部分。不过，路由虽然简化了，但预示着实现的过程需要用到更高级的技术，而不会降低代码的复杂度。从<a href="chapter2.html#a-toy-app">第 2 章</a>起我们就十分依赖脚手架，不过现在我们将舍弃脚手架的大部分功能。</p>
<div id="listing-microposts-resource" data-type="listing">
<h5><span class="title-label">代码清单 11.29</span>：微博资源的路由设置</h5>
<div class="source-file">config/routes.rb</div>
<div class="highlight language-ruby"><pre><span class="no">Rails</span><span class="o">.</span><span class="n">application</span><span class="o">.</span><span class="n">routes</span><span class="o">.</span><span class="n">draw</span> <span class="k">do</span>
<span class="n">root</span> <span class="s1">'static_pages#home'</span>
<span class="n">get</span> <span class="s1">'help'</span> <span class="o">=></span> <span class="s1">'static_pages#help'</span>
<span class="n">get</span> <span class="s1">'about'</span> <span class="o">=></span> <span class="s1">'static_pages#about'</span>
<span class="n">get</span> <span class="s1">'contact'</span> <span class="o">=></span> <span class="s1">'static_pages#contact'</span>
<span class="n">get</span> <span class="s1">'signup'</span> <span class="o">=></span> <span class="s1">'users#new'</span>
<span class="n">get</span> <span class="s1">'login'</span> <span class="o">=></span> <span class="s1">'sessions#new'</span>
<span class="n">post</span> <span class="s1">'login'</span> <span class="o">=></span> <span class="s1">'sessions#create'</span>
<span class="n">delete</span> <span class="s1">'logout'</span> <span class="o">=></span> <span class="s1">'sessions#destroy'</span>
<span class="n">resources</span> <span class="ss">:users</span>
<span class="n">resources</span> <span class="ss">:account_activations</span><span class="p">,</span> <span class="ss">only</span><span class="p">:</span> <span class="o">[</span><span class="ss">:edit</span><span class="o">]</span>
<span class="n">resources</span> <span class="ss">:password_resets</span><span class="p">,</span> <span class="ss">only</span><span class="p">:</span> <span class="o">[</span><span class="ss">:new</span><span class="p">,</span> <span class="ss">:create</span><span class="p">,</span> <span class="ss">:edit</span><span class="p">,</span> <span class="ss">:update</span><span class="o">]</span>
<span class="hll"> <span class="n">resources</span> <span class="ss">:microposts</span><span class="p">,</span> <span class="ss">only</span><span class="p">:</span> <span class="o">[</span><span class="ss">:create</span><span class="p">,</span> <span class="ss">:destroy</span><span class="o">]</span>
</span><span class="k">end</span>
</pre></div>
</div>
<table id="table-restful-microposts" class="tableblock frame-all grid-all" style="width: 100%;">
<caption><span class="title-label">表 11.2</span>：<a href="#listing-microposts-resource">代码清单 11.29</a> 设置的微博资源路由</caption>
<colgroup>
<col style="width: 25%;" />
<col style="width: 25%;" />
<col style="width: 25%;" />
<col style="width: 25%;" />
</colgroup>
<thead>
<tr>
<th class="tableblock halign-left valign-top">HTTP 请求</th>
<th class="tableblock halign-left valign-top">URL</th>
<th class="tableblock halign-left valign-top">动作</th>
<th class="tableblock halign-left valign-top">作用</th>
</tr>
</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>POST</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">/microposts</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>create</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">创建新微博</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>DELETE</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">/microposts/1</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>destroy</code></p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">删除 ID 为 1 的微博</p></td>
</tr>
</tbody>
</table>
<section data-type="sect2" id="access-control">
<h2><span class="title-label">11.3.1</span> 访问限制</h2>
<p>开发微博资源的第一步，我们要在微博控制器中实现访问限制：若想访问 <code>create</code> 和 <code>destroy</code> 动作，用户要先登录。</p>
<p>针对这个要求的测试和用户控制器中相应的测试类似（<a href="chapter9.html#listing-edit-update-redirect-tests">代码清单 9.17</a> 和<a href="chapter9.html#listing-action-tests-admin">代码清单 9.56</a>），我们要使用正确的请求类型访问这两个动作，然后确认微博的数量没有变化，而且会重定向到登录页面，如<a href="#listing-create-destroy-micropost-tests">代码清单 11.30</a> 所示。</p>
<div id="listing-create-destroy-micropost-tests" data-type="listing">
<h5><span class="title-label">代码清单 11.30</span>：微博控制器的访问限制测试 <span class="red">RED</span></h5>
<div class="source-file">test/controllers/microposts_controller_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">MicropostsControllerTest</span> <span class="o"><</span> <span class="no">ActionController</span><span class="o">::</span><span class="no">TestCase</span>
<span class="k">def</span> <span class="nf">setup</span>
<span class="vi">@micropost</span> <span class="o">=</span> <span class="n">microposts</span><span class="p">(</span><span class="ss">:orange</span><span class="p">)</span>
<span class="k">end</span>
<span class="nb">test</span> <span class="s2">"should redirect create when not logged in"</span> <span class="k">do</span>
<span class="n">assert_no_difference</span> <span class="s1">'Micropost.count'</span> <span class="k">do</span>
<span class="n">post</span> <span class="ss">:create</span><span class="p">,</span> <span class="ss">micropost</span><span class="p">:</span> <span class="p">{</span> <span class="ss">content</span><span class="p">:</span> <span class="s2">"Lorem ipsum"</span> <span class="p">}</span>
<span class="k">end</span>
<span class="n">assert_redirected_to</span> <span class="n">login_url</span>
<span class="k">end</span>
<span class="nb">test</span> <span class="s2">"should redirect destroy when not logged in"</span> <span class="k">do</span>