Twig Components / Methods / iterable

iterable is a Twig test to check if a variable is an array or a traversable object:

{# evaluates to true if the foo variable is iterable #}
{% if users is iterable %}
    {% for user in users %}
        Hello {{ user }}!
    {% endfor %}
{% else %}
    {# users is probably a string #}
    Hello {{ users }}!
{% endif %}

Source: Twig