if condition on empty string

[etienneroudeix]

Hello, I was just wanting to test if my_variable was an empty string.

I'm using Liquid through Jekyll if it can help.

I tried :

{% if my_variable == '' %}
I'm not empty
{% endif %}

but no way.

In fact I have to do like this

{% if my_variable == %}
I'm not empty
{% endif %}

It sound ugly to me so I let you know.

By the way it's the same behaviour using case condition.

Thank you for your job on this rocking project.

[nickpearson]

You can use the blank keyword: {% if my_variable == blank %}, which internally checks my_variable.blank?. See the 'blank' entry in the LITERALS hash if you're curious about how it works.

[etienneroudeix]

Hi, thank you for your response !
Kind regards.

[etienneroudeix]

Well, I just tested :

{% if my_variable == blank %}
I'm not empty
{% endif %}

and

{% if my_variable.blank? %}
I'm not empty
{% endif %}

And none of them behave as it should :(

[nickpearson]

What is the exact output of this?

my_variable is {% if my_variable == blank %}blank{% else %}"{{ my_variable }}"{% endif %}

This will result in one of the following:

my_variable is blank
my_variable is "something"

Also, to make your logic match up, you'll either want to change == to != or remove "not" from "I'm not empty".

Sorry if I wasn't clear -- the .blank? is what Liquid uses internally (in its Ruby code) -- you can't actually call my_variable.blank? in your Liquid code (unless you've added a custom blank? Liquid method to whatever class my_variable is).

[fw42]

Shit, that might be a bug. "blank?" is not a Ruby thing but Rails. If you use Jekyll, that might not work. Not sure though.

[nickpearson]

True. empty is also in there (aliases to :empty?). @etienneroudeix, this is standard Ruby (doesn't depend on Rails), but it behaves different from blank?, so be careful when using it on strings:

# same
"".blank? #=> true
"".empty? #=> true

# different
"  ".blank? #=> true
"  ".empty? #=> false

[fw42]

I can't reproduce the bug. This:

{% assign my_variable = '' %}
{% if my_variable == '' %} works {% endif %}

works for me.

[fw42]

Do you want to test on the variable being the empty string or do you want to test on it being defined? Try testing for nil instead maybe?

[etienneroudeix]

WOW lot of passionate talking thank you.

my_variable is {% if my_variable == blank %}blank{% else %}"{{ my_variable }}"{% endif %} gave me :

my_variable is ""

and my_variable is {% if my_variable == empty %}empty{% else %}"{{ my_variable }}"{% endif %} gave me the same exactly.

I want to test an empty (not even a space) or unset string

my_variable is {% if my_variable == nil %}nil{% else %}"{{ my_variable }}"{% endif %} works fine when the variable is not define.

But I still only can test empty string like that : my_variable is {% if my_variable == %}blank or not set{% else %}"{{ my_variable }}"{% endif %}

Thanks

[etienneroudeix]

Well my bad !

my_variable is {% if my_variable == %}blank or not set{% else %}"{{ my_variable }}"{% endif %}

does not work with empty string. It just behave exactly like nil testing.

[fw42]

How about {% if my_variable == "" or my_variable == nil %}?

[etienneroudeix]

Excellent ! It works !

Thank you very much !

To let you know :
if my_variable == blank or my_variable == nil
does not works.

My problem is solved thank you !

[chrishough]

In case anyone comes across this thread, I had to add 1 more piece to the conditional to make it work:

{% if post.image_thumbnail_500x500 And post.image_thumbnail_500x500 != "" And post.image_thumbnail_500x500 != nil %}
  <img src="{{ post.image_thumbnail_500x500 | asset_path }}">
{% endif %}