同样，如何检查是否在Twig模板上定义了var

Question

I have this code at Twig template:

{% if form_action is empty or form_action is null or form_action is not defined %}
    {% set form_action = '' %}
{% endif %}

But when I load the page I got this error message:

Variable "form_action" does not exist in AppBundle::pdone.html.twig at line 1

How do I check also if variable is set? Is not the condition enough? Any advice?

Answer 1

The order of your statement is not correct. Usually this should be enough:

{% if form_action is not defined %}

to see if a variable has a value:

{% if form_action %}

Answer 2

Use is defined

{% if form_action is defined %}
 {# Do your stuff here #}
{% endif %}