Control flow

Control flow tags create conditions that decide whether blocks of Liquid code get executed.

if

Executes a block of code only if a certain condition is true.

Input

{% if product.title == "Awesome Shoes" %}
  These shoes are awesome!
{% endif %}

Output

These shoes are awesome!

unless

The opposite of if – executes a block of code only if a certain condition is not met.

Input

{% unless product.title == "Awesome Shoes" %}
  These shoes are not awesome.
{% endunless %}

Output

These shoes are not awesome.

This would be the equivalent of doing the following:

{% if product.title != "Awesome Shoes" %}
  These shoes are not awesome.
{% endif %}

elsif / else

Adds more conditions within an if or unless block.

Input

<!-- If customer.name = "anonymous" -->
{% if customer.name == "kevin" %}
  Hey Kevin!
{% elsif customer.name == "anonymous" %}
  Hey Anonymous!
{% else %}
  Hi Stranger!
{% endif %}

Output

Hey Anonymous!

case/when

Creates a switch statement to execute a particular block of code when a variable has a specified value. case initializes the switch statement, and when statements define the various conditions.

A when tag can accept multiple values. When multiple values are provided, the expression is returned when the variable matches any of the values inside of the tag. Provide the values as a comma-separated list, or separate them using an or operator.

An optional else statement at the end of the case provides code to execute if none of the conditions are met.

Input

{% assign handle = "cake" %}
{% case handle %}
  {% when "cake" %}
     This is a cake
  {% when "cookie", "biscuit" %}
     This is a cookie
  {% else %}
     This is not a cake nor a cookie
{% endcase %}

Output

This is a cake

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Blank or non-existent values

This syntax allows you to manage blank and non-existent variables:

{% if Variables.<variableName> == blank}
 <value for non-blank>
 {% if Variables.<variableName> == blank}
 <value for non-blank>
 {% else %}
 <value for blank>
{% endif %}

Example:

{% if Variables.JobNumber == blank}
  Job: {{Variables.JobNumber}}
 {% if Variables.JobNumber == blank}
  Job: {{Variables.JobNumber}}
 {% else %}
  Job is undefined
{% endif %}