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    <h1><a href="http://wbowam.github.io/django-validators.html"> Django Validators  </a></h1>
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            <p>之前没用过Validators <br />
这回入了门，用了一下，很爽～～    </p>
<hr />
<p><a href="https://docs.djangoproject.com/en/dev/ref/validators/">Django Validators</a>   </p>
<h5 id="djangovalidators">正如django文档所说：我们可以自己新建各种Validators，如：<a class="headerlink" href="#djangovalidators" title="Permanent link">&para;</a></h5>
<div class="highlight"><pre><span class="n">from</span> <span class="n">django</span><span class="p">.</span><span class="n">core</span><span class="p">.</span><span class="n">exceptions</span> <span class="n">import</span> <span class="n">ValidationError</span>

<span class="n">def</span> <span class="n">validate_even</span><span class="p">(</span><span class="n">value</span><span class="p">)</span><span class="o">:</span>
    <span class="k">if</span> <span class="n">value</span> <span class="o">%</span> <span class="mi">2</span> <span class="o">!=</span> <span class="mi">0</span><span class="o">:</span>
        <span class="n">raise</span> <span class="n">ValidationError</span><span class="p">(</span><span class="err">&#39;</span><span class="o">%</span><span class="n">s</span> <span class="n">is</span> <span class="n">not</span> <span class="n">an</span> <span class="n">even</span> <span class="n">number</span><span class="err">&#39;</span> <span class="o">%</span> <span class="n">value</span><span class="p">)</span>
</pre></div>


<p>You can add this to a model field via the field’s validators argument:   </p>
<div class="highlight"><pre><span class="n">from</span> <span class="n">django</span><span class="p">.</span><span class="n">db</span> <span class="n">import</span> <span class="n">models</span>

<span class="n">class</span> <span class="n">MyModel</span><span class="p">(</span><span class="n">models</span><span class="p">.</span><span class="n">Model</span><span class="p">)</span><span class="o">:</span>
    <span class="n">even_field</span> <span class="o">=</span> <span class="n">models</span><span class="p">.</span><span class="n">IntegerField</span><span class="p">(</span><span class="n">validators</span><span class="o">=</span><span class="p">[</span><span class="n">validate_even</span><span class="p">])</span>
</pre></div>


<p>神奇点在于，django自动帮我们抓取‘值’当作参数传入我们的Validators（有点像让人讨厌的黑魔术，但不是～～）    </p>
<h5 id="validatorsformmodelform">同一个Validators也可以用于form，因为model和form相应的机理是一样的<a class="headerlink" href="#validatorsformmodelform" title="Permanent link">&para;</a></h5>
<div class="highlight"><pre><span class="n">from</span> <span class="n">django</span> <span class="n">import</span> <span class="n">forms</span>

<span class="n">class</span> <span class="n">MyForm</span><span class="p">(</span><span class="n">forms</span><span class="p">.</span><span class="n">Form</span><span class="p">)</span><span class="o">:</span>
    <span class="n">even_field</span> <span class="o">=</span> <span class="n">forms</span><span class="p">.</span><span class="n">IntegerField</span><span class="p">(</span><span class="n">validators</span><span class="o">=</span><span class="p">[</span><span class="n">validate_even</span><span class="p">])</span>
</pre></div>


<h3 id="validatorsbuilt-in-validators">不过，多数时候我们喜欢用内置的Validators，也就是官网说的<code>Built-in validators</code><a class="headerlink" href="#validatorsbuilt-in-validators" title="Permanent link">&para;</a></h3>
<p>用法如下:</p>
<div class="highlight"><pre><span class="n">from</span> <span class="n">django</span><span class="p">.</span><span class="n">core</span><span class="p">.</span><span class="n">validators</span> <span class="n">import</span> <span class="n">MinLengthValidator</span>
<span class="n">from</span> <span class="n">django</span><span class="p">.</span><span class="n">db</span> <span class="n">import</span> <span class="n">models</span>

<span class="n">class</span> <span class="n">MyModel</span><span class="p">(</span><span class="n">models</span><span class="p">.</span><span class="n">Model</span><span class="p">)</span><span class="o">:</span>
    <span class="n">even_field</span> <span class="o">=</span> <span class="n">models</span><span class="p">.</span><span class="n">TextField</span><span class="p">(</span><span class="n">validators</span><span class="o">=</span><span class="p">[</span><span class="n">MinLengthValidator</span><span class="p">(</span><span class="mi">20</span><span class="p">)])</span>
</pre></div>


<p>以上所用<code>MinLengthValidator</code>网名生意：<code>max_length</code>的反意思。  <br />
还有很多内置Validator，<a href="https://docs.djangoproject.com/en/dev/ref/validators/">看官网</a></p>
<h3 id="validator">假如我想改一下内置 Validator的错误提示，可以这么干：<a class="headerlink" href="#validator" title="Permanent link">&para;</a></h3>
<p>1.自己写一个子类，覆盖message</p>
<div class="highlight"><pre><span class="n">from</span> <span class="n">django</span><span class="p">.</span><span class="n">core</span><span class="p">.</span><span class="n">validators</span> <span class="n">import</span> <span class="n">MinLengthValidator</span>
<span class="n">from</span> <span class="n">django</span><span class="p">.</span><span class="n">db</span> <span class="n">import</span> <span class="n">models</span>

<span class="n">class</span> <span class="n">MyMinLengthValidator</span><span class="p">(</span><span class="n">MinLengthValidator</span><span class="p">)</span><span class="o">:</span>
    <span class="n">message</span> <span class="o">=</span> <span class="s">&quot;少年， 至少输入%(limit_value)d个字符 ，(你怎么只输入 %(show_value)d个字符就完事儿啊).&quot;</span>

<span class="n">class</span> <span class="n">MyModel</span><span class="p">(</span><span class="n">models</span><span class="p">.</span><span class="n">Model</span><span class="p">)</span><span class="o">:</span>
    <span class="n">even_field</span> <span class="o">=</span> <span class="n">models</span><span class="p">.</span><span class="n">TextField</span><span class="p">(</span><span class="n">validators</span><span class="o">=</span><span class="p">[</span><span class="n">MinLengthValidator</span><span class="p">(</span><span class="mi">20</span><span class="p">)])</span>
</pre></div>


<ol>
<li>当然，这种方法很简单，很常见，不够高大上：填写<code>error_messages</code>选项</li>
</ol>
<div class="highlight"><pre><span class="p">....</span>
<span class="n">my_field</span> <span class="o">=</span> <span class="n">forms</span><span class="p">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">validators</span><span class="o">=</span><span class="p">[</span><span class="n">MinLengthValidator</span><span class="p">(</span><span class="mi">8</span><span class="p">)],</span>
                           <span class="n">error_messages</span><span class="o">=</span><span class="p">{</span><span class="s">&quot;min_length&quot;</span><span class="o">:</span><span class="s">&quot;少年， 至少输入%(limit_value)d个字符 ，(你怎么只输入 %(show_value)d个字符就完事儿啊).&quot;</span><span class="p">})</span>
<span class="p">})</span>
<span class="p">..</span>  <span class="p">.</span> <span class="p">..</span>
</pre></div>
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            <h4>Published</h4>
            <time pubdate="pubdate" datetime="2014-09-07T00:00:00+08:00">Sep 7, 2014</time>
            <h4>Category</h4>
            <a class="category-link" href="/categories.html#It-ref">It</a>
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