defined
¶
defined
检查变量是否在当前上下文中定义。如果您使用 strict_variables
选项:
1 2 3 4 5 6 7 8 9 10 11 12 13 | {# defined works with variable names #}
{% if foo is defined %}
...
{% endif %}
{# and attributes on variables names #}
{% if foo.bar is defined %}
...
{% endif %}
{% if foo['bar'] is defined %}
...
{% endif %}
|
当使用 defined
测试在某些方法调用中使用变量的表达式,请确保首先定义了所有变量:
1 2 3 | {% if var is defined and foo.method(var) is defined %}
...
{% endif %}
|