How to check for null in Twig?

Question

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

Answer 1

Depending on what exactly you need:

• is null checks whether the value is null:

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

• is defined checks whether the variable is defined:

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

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 %}