if

Selects an argument depending on a condition.

For example:

{{ value|if:"yes":"no" }}

This is a shortcut for using the if tag. The same can be expressed as follows:

{% if value %}yes{% else %}no{% endif %}

Note that falsy values (0, false, undefined or empty string) evaluate to false.

Elaborate examples

{% with is_i18n|if:r.translation[lang_code].body:r.body as body %}

So if is_i18n evaluates to true, body is assigned to r.translation[lang_code].body, else to r.body.

{% include "_language_attrs.tpl" id=pid class=(pid==id)|if:"active":"" %}

Add parameter class to the included template; when pid equals id, class is "active", otherwise an empty string.