Does Twig have a null coalesce operator?

Question

I'm using the Twig PHP template engine.

Is there an operator available which will output first non-empty value (coalesce)?

For example (using PHP pseudocode):

{{ title ?: "Default Title" }}

I know I could do something like this, but it's a bit long-winded:

{% if title %}{{ title }}{% else %}{{ "Default Title" }}{% endif %}

The answer is provided by @molecularman but I want to let you know you can make your last example shorter: `{{ title ? title : 'Default Title' }}` — Wouter J, Nov 19 '12 at 20:38

score 57 · Answer 1 · answered Oct 24 '16 at 04:44

The null-coalescing operator was formally introduced in Twig 1.24 (Jan. 25, 2016).

* adding support for the ?? operator

Which means it's now possible to do this...

{{ title ?? "Default Title" }}

You can even chain them together, to check multiple variables until a valid non-null value is found.

{{ var1 ?? var2 ?? var3 ?? var4 }}

score 33 · Accepted Answer · answered Nov 19 '12 at 13:43

33

Yes, there is this filter called default. You can apply it to your code like below:

{{ title|default("Default Title") }}

answered Nov 19 '12 at 13:43

Molecular Man

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This is incorrect, `default` performs a boolean-like evaluation, which e.g. means the non-null-value `false` will also be replaced with the default value. As of Twig v1.24 better use the `??` operator. See https://twig.symfony.com/doc/2.x/tests/empty.html – Hudri Oct 29 '20 at 17:50
Thanks for the info. However, the link to the documentation that you shared is broken. Try this instead: https://twig.symfony.com/doc/2.x/filters/default.html – Matthew Setter Apr 15 '23 at 06:41

mpen · Answer 3 · 2019-01-16T22:25:37.590

6

As of Twig 1.12.0, it does have the ?: operator, but it's not really "null coalescing". It checks for truthiness, not just nulls, thus 0 ?: 1 would come out 1.

Documentation

edited Jan 16 '19 at 22:25

answered Dec 02 '14 at 23:01

mpen

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Does Twig have a null coalesce operator?

3 Answers3