doc/filters/default.rst
defaultThe default filter returns the passed default value if the value is
undefined or empty, otherwise the value of the variable:
.. code-block:: twig
{{ var|default('var is not defined') }}
{{ user.name|default('name item on user is not defined') }}
{{ user['name']|default('name item on user is not defined') }}
{{ ''|default('passed var is empty') }}
When using the default filter on an expression that uses variables in some
method calls, be sure to use the default filter whenever a variable can be
undefined:
.. code-block:: twig
{{ user.value(name|default('username'))|default('not defined') }}
Using the default filter on a boolean variable might trigger unexpected
behavior, as false is treated as an empty value. Consider using ??
instead:
.. code-block:: twig
{% set value = false %}
{{ value|default(true) }} {# true #}
{{ value ?? true }} {# false #}
.. note::
Read the documentation for the :doc:`defined<../tests/defined>` and
:doc:`empty<../tests/empty>` tests to learn more about their semantics.
default: The default value