Answers for "twig is defined"

twig is set variable

{# defined works with variable names #}
{% if foo is defined %}
    ...
{% endif %}

{# and attributes on variables names #}
{% if foo.bar is defined %}
    ...
{% endif %}

{% if foo['bar'] is defined %}
    ...
{% endif %}

twig variable is defined

{% if varname is defined %}
	Variable exists.
{% endif %}