In Twig, check if a specific key of an array exists
PhpArraysTwigConditionalShort CircuitingPhp Problem Overview
In PHP we can check if a key exists in an array by using the function array_key_exists().
In the Twig templating language we can check if an variable or an object's property exists simply by using an if statement, like this:
{% if app.user %}
do something here
{% else %}
do something else
{% endif %}
But how do we check if a key of an array exists using Twig? I tried {% if array.key %}, but it gives me an error:
Key "key" for array with keys "0, 1, 2, 3...648" does not exist
As one of the primary ways of passing data into a template is using arrays, it seems like there should be some way of doing this. Any thoughts?
Php Solutions
Solution 1 - Php
Twig example:
{% if array.key is defined %}
// do something
{% else %}
// do something else
{% endif %}
Solution 2 - Php
You can use the keys twig function
{% if myVar in someOtherArray|keys %}
Solution 3 - Php
Quick Answer (TL;DR)
- DeveloperTLindel wants to test for existence of array key in Twig.
- DeveloperTLindel wants to trap any errors associated with undefined key.
- This can be handled using the
defaultfilter.
Detailed Answer
Context
- Twig 2.x (latest version as of Wed 2017-03-08)
- General-purpose use of the
defaultfilter.
Problem
-
Scenario:
-
DeveloperTLindel wants to test for existence of array key in Twig.
-
DeveloperTLindel wants to avoid any errors or exceptions caused by potentially undefined key.
Solution
- DeveloperTLindel can use the
defaultfilter. - The
defaultfilter catches any exceptions owing to undefined variable, and allows short-circuit substition of an alternate value. - The
defaultfilter is chainable.
Example01
{#- **************************************** testing for a single key in associative array -#} {%- set mystring = myarray['key-no-existo'] |default('BLANK') -%}
{#- **************************************** testing for a multiple keys in associative array -#} {%- set mystring = myarray['alpha'] |default(myarray['bravo']) |default(myarray['charlie']) |default('BLANK') -%}