Ternary concatenation in Twig

Question

Is it possible to use ternary operator in Twig when concatenating one string to another if some condition is true?

This works for me:

{% set a = 'initial' %} {% if foo == bar %} {% set a = a ~ ' concatenate' %} {% endif %} <p>{{ a }}</p>

But when I try to simplify it like this, it throws an error:

{% set a = 'initial' ~ (foo == bar) ? ' concatenate' : '' %} <p>{{ a }}</p>

Am I doing something wrong or this simplification is simply not possible in Twig?

DarkBee · Accepted Answer · 2019-04-19 07:44:02Z

due to the order of precedence you'll need to add parentheses,
{% set a = 'initial' ~ ((foo == bar) ? ' concatenate' : '') %}

If the 2nd part is empty you can even omit it e.g.

{% set b = 'initial' ~ ((foo == foo) ? ' concatenate') %}

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