Liquid Tags: Flow Control

• If/Else
• Operators
• Boolean Operators
• Types and Truthiness
• Case Statement

If/Else

if / else statements should be similar to other programming languages. Liquid implements them with the following tags:

• : Encloses a section of a template that will only be run if the condition is true.
• : Can optionally be used within an ... block. Specifies another condition; if the initial 'if' fails, Liquid tries the 'elsif' and runs the following section of the template if it succeeds. You can use any number of elsifs in an if block.
• : Can optionally be used within an ... block, after any 'elsif' tags. If all preceding conditions fail, Liquid will run the section of the template following the 'else' tag.
• : The reverse of an 'if' statement. Don't use 'elsif' or 'else' with an unless statement.

The condition of an if, elsif, or unless tag should be either a normal Liquid expression or a comparison using Liquid expressions. Note that the comparison operators are implemented by the 'if'-like tags; they don't work anywhere else in Liquid.

Operators

The available comparison operators are:

• , and : equality and inequality ( and mean the same thing)
• , , , : less/greater-than
• There are also special values and (unquoted) that you can compare arrays to; the comparison is if the array has no members.
• : similar to Ruby's method, implemented on strings, arrays, and hashes. If the left argument is a string and the right isn't, it stringifies the right.

Boolean Operators

The available Boolean operators are:

You can use the and operators to include more than one condition in a control flow tag. and can be chained together to create complex conditionals.

If you use more than one or , Liquid checks them from right to left. For example, means . You cannot use parentheses to change the order. Parentheses are invalid characters within Liquid tags and prevent your tags from working.

and

The operator lets you add additional conditions to a tag. A condition with an will only be true if both the condition's left and right sides are true.

Input

{% if line_item.grams > 20000 and customer_address.city == "Ottawa"%} 
You're buying a heavy item, and are in the same city as our store. Choose local pick-up as a shipping option to avoid paying high shipping costs. 
{% endif %}

Output

You're buying a heavy item, and are in the same city as our store. Choose local pick-up as a shipping option to avoid paying high shipping costs.

or

The operator lets you add additional conditions to a tag. A condition with an will be true if either the condition's left or right side is true.

{% if customer.tags contains "VIP" or customer.email contains "mycompany.com" %}
  Welcome! We're pleased to offer you a special discount of 15% on all products.
{% else %}
  Welcome to our store!
{% endif %}

Output

Welcome! We're pleased to offer you a special discount of 15% on all products.

Types and Truthiness

Liquid expressions are tested for 'truthiness' in a Ruby-like way:

{% if user %}
  Hello {{ user.name }}
{% endif %}

{% comment %} Same as above {% endcomment %}
{% if user != null %}
  Hello {{ user.name }}
{% endif %}

{% if user.name == "tobi" %}
  Hello tobi
{% elsif user.name == "bob" %}
  Hello bob
{% endif %}

{% if user.name == "tobi" or user.name == "bob" %}
  Hello tobi or bob
{% endif %}

{% if user.name == "bob" and user.age > 45 %}
  Hello old bob
{% endif %}

{% if user.name != "tobi" %}
  Hello non-tobi
{% endif %}

{% comment %} Same as above {% endcomment %}
{% unless user.name == "tobi" %}
  Hello non-tobi
{% endunless %}


{% comment %} Check for the size of an array {% endcomment %}
{% if user.payments == empty %}
  you never paid !
{% endif %}

{% if user.payments.size > 0  %}
  you paid !
{% endif %}

{% if user.age > 18 %}
  Login here
{% else %}
  Sorry, you are too young
{% endif %}

{% comment %} array = 1,2,3 {% endcomment %}
{% if array contains 2 %}
  array includes 2
{% endif %}

{% comment %} string = "hello world" {% endcomment %}
{% if string contains "hello" %}
  string includes "hello"
{% endif %}

Case Statement

If you need more conditions, you can use the statement:

{% case condition %}
{% when 1 %}
  hit 1
{% when 2 or 3 %}
  hit 2 or 3
{% else %}
  ... else ...
{% endcase %}

Example:

{% case template %}

{% when "label" %}
  {{ label.title }}
{% when "product" %}
  {{ product.vendor }} / {{ product.title }}
{% else %}
  {{ page_title }}
{% endcase %}

Try it

Edit the input and press Run. The example runs on this site, read-only.