我应该使用什么构造来检查 Twig 模板中的值是否为 NULL?

What construct should I use to check whether a value is NULL in a Twig template?

推荐答案

取决于你到底需要什么:

Depending on what exactly you need:

is null 检查是否值为 null:

{% if var is null %}
    {# do something #}
{% endif %}

is defined 检查是否变量已定义:

is defined checks whether the variable is defined:

{% if var is not defined %}
    {# do something #}
{% endif %}

另外，is sameas 测试，其中对两个值进行类型严格比较，可能对检查 null 以外的值(如 false)感兴趣:

Additionally the is sameas test, which does a type strict comparison of two values, might be of interest for checking values other than null (like false):

{% if var is sameas(false) %}
    {# do something %}
{% endif %}