CODEWITHSUNDEEP
phpsymfonytwig
Joe
Joe

Reputation: 2436

A NULL check in Twig Template is not working which leads to an error (very strange behavior)

I’m currently facing a very strange problem in a Twig template (Symfony v2.8.9; Twig v1.24.1). The basic outline is: I’m trying to overwrite a block in a child template when a specific condition is met.

Here’s a snippet of my template:

{% extends "@App/search/resultList.html.twig" %}

{% if category.teaser %}
  {% block description %}{{category.teaser.doSomething()}}{% endblock %}
{% endif %}

This code leads to the following error:

Impossible to invoke a method ("doSomething") on a null variable in @App/search/categoryResult.html.twig

The teaser property of the category indeed is null, which is okay and what the check is for.

I also tried an explicit {% if category.teaser is not null %} which also didn’t work and resulted in the same error.

Now for the really weird part (or maybe I’m just not seeing it why this wouldn’t be weird):

If I change the code to

{% block description %}
  {% if category.teaser %}
    {{category.teaser.doSomething()}}
  {% endif %}
{% endblock %}

it works as intended (mostly, at least, because the parent block will always be overwritten).

This error seems to happen only in the Symfony dev environment.

It seems:

# Twig Configuration
twig:
    debug:            true
    strict_variables: true

has something to do with it, which explains the dev environment only. If both values are set to false it works correctly.

Has anybody ever encountered a problem like this and solved it? Any help in solving this issue would be much appreciated.

Upvotes: 1

Views: 805

Answers (2)

W. Bilel
W. Bilel

Reputation: 291

You have done the best practice by testing whether the variable is null or not. In many other languages you can’t do something on a null. You can use the dump() function to check your variables.

Upvotes: -2

Uwe J
Uwe J

Reputation: 46

As far as I know, it is not possible to conditionally override a block in twig, see also How can I conditionally override a TWIG layout block?

Upvotes: 3

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