TWIG的 tests 学习

{{ var is odd }} <br><pre name="code" class="html">{{ var is odd }}
<p> </p>
<p> </p>
<p>sameas<br>
检查变量的地址是否相同</p>
<p>{% if foo.attribute is sameas(false) %} <br>
    the foo attribute really is the ``false`` PHP value <br>
{% endif %} <br>
{% if foo.attribute is sameas(false) %}<br>
    the foo attribute really is the ``false`` PHP value<br>
{% endif %}</p>
<p> </p>
<p>constant<br>
检查变量的值是否相同</p>
<p>{% if post.status is constant('Post::PUBLISHED') %} <br>
    the status attribute is exactly the same as Post::PUBLISHED <br>
{% endif %} <br>
{% if post.status is constant('Post::PUBLISHED') %}<br>
    the status attribute is exactly the same as Post::PUBLISHED<br>
{% endif %}</p>
<p> </p>
<p>defined<br>
测试变量是否定义</p>
<p>{# defined works with variable names #} <br>
{% if foo is defined %} <br>
    ... <br>
{% endif %} <br>
 <br>
{# and attributes on variables names #} <br>
{% if foo.bar is defined %} <br>
    ... <br>
{% endif %} <br>
 <br>
{% if foo['bar'] is defined %} <br>
    ... <br>
{% endif %} <br>
{# defined works with variable names #}<br>
{% if foo is defined %}<br>
    ...<br>
{% endif %}</p>
<p>{# and attributes on variables names #}<br>
{% if foo.bar is defined %}<br>
    ...<br>
{% endif %}</p>
<p>{% if foo['bar'] is defined %}<br>
    ...<br>
{% endif %}</p>
<p> </p>
<p>empty<br>
测试变量是否为空，empty的意思是：该变量已经定义，但他的值是 null false 或者是空字符串<br>
{# evaluates to true if the foo variable is null, false, or the empty string #} <br>
{% if foo is empty %} <br>
    ... <br>
{% endif %} <br><br>
摘自 jiaochangyun的专栏</p>