Check if string variable is null or empty, or full of white spaces

Question

How can I check if a string variable is null or empty, or full with space characters in Twig? (Shortest possible, maybe an equivalent to CSharp's String.IsNullOrWhiteSpace() method)

Answer 1

There are already good answers, but I give my 2 cents too:

{% if foo|length %}

I was inspired by @GuillermoGutiérrez's filter trick.

But I think |length is safer as the "0"|trim expression will evaluates to false.

References :

• length
• codepad
• boolval