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Introduction to Liquid

Liquid markup language is an open-source template language created by Shopify and written in Ruby. In the context of our plugins, it is used to create templates for custom invoices or issue reports.


There are two types of markup in liquid: Output and Tag.

  • Output is surrounded by {{ two curly brackets }}
  • Output blocks will always be replaced with the data which they reference.
  • For instance, if your liquid template has a company object exposed to it, you can print the name of the company to the screen by referencing {{ }}
  • Tags are surrounded by {% a curly bracket and a percent %}
  • Tags drive the logic of templates. They are responsible for loops and branching logic such as If / Else.


Here is a simple example of Output:

Hello {{name}}

Hello {{}}
Hello {{ 'seth' }}

Output filters

Output markup takes filters. Filters are simple methods. The first parameter is always the output of the left side of the filter. The return value of the filter will be the new left value when the next filter is run. When there are no more filters the template will receive the resulting string.

Hello {{ 'seth' | upcase }}
Hello seth has {{ 'seth' | length }} letters!
Hello {{ '*seth*' | format_text | upcase }}
Hello {{ 'now' | format_date }}

Standard Liquid Filters

date reformat a date (syntax reference)
capitalize capitalize words in the input sentence
downcase convert an input string to lowercase
upcase convert a input string to uppercase
first get the first element of the passed in array
last get the last element of the passed in array
join join elements of the array with certain character between them
sort sort elements of the array
size return the size of an array or string
strip_html strip html from string
strip_newlines strip all newlines (\n) from string
newline_to_br replace each newline (\n) with html break
replace replace each occurrence Ex:
{{ foofoo | replace:foo, bar }} #=> barbar 
replace_first replace the first occurrence Ex:
{{ barbar | replace_first:bar,foo }} #=> foobar 
remove remove each occurrence Ex:
{{ foobarfoobar | remove:foo }} #=> barbar 
remove_first remove the first occurrence Ex:
{{ barbar | remove_first:bar }} #=> bar 
truncate truncate a string down to x characters
truncatewords truncate a string down to x words
prepend prepend a string Ex:
{{ bar | prepend:foo }} #=> foobar 
append append a string Ex:
{{ foo | append:bar }} #=> foobar 
minus subtraction e.g
{{ 4 | minus:2 }} #=> 2 
plus addition e.g
{{ 1 | plus:1 }} #=> 11
{{ 1 | plus:1 }} #=> 2 
times multiplication e.g
{{ foo | times:4 }} #=> foofoofoofoo
{{ 5 | times:4 }} #=> 20 
divided_by division e.g
{{ 10 | divided_by:2 }} #=> 5 

RedmineCRM specific filters

underscore replace spaces and slashes to '_'
dasherize replace spaces and slashes to '-'
multi_line replace end of line in text to
rjust right justify and padd a string
ljust left justify and padd a string
textile textiliaze a string
currency formats number as a currency Ex:
{{ 100 | currency: USD }} #=> $100.00 
custom_field return object custom field value Ex:
{{ invoice | custom_field: "Test custom field" }}
#=> <Test custom field value> 

To use a custom field value inside a logical construct(if/else, loop), assign its value to a variable first:
{% assign value = invoice | custom_field: "Test custom field"%}
{% if value == ...
attachment return disk file name of object attachment Ex:
{{ invoice | attachment: "test.jpg" }}
#=> /var/www/redmine/files/12314234_test.jpg 


Tags are how you can include logic in your template. Below are the tags available to you inside Cashboard.

Variable Assignment

You can store data in your own variables, to be used in output or other tags as desired. The simplest way to create a variable is with the assign tag, which has a pretty straightforward syntax:

{% assign name = 'freestyle' %}
{% for t in collections.tags %}
  {% if t == name %}
  {% endif %}
{% endfor %}

Another way of doing this would be to assign true/false values to the variable:

{% assign freestyle = false %}
{% for t in collections.tags %}{% if t == 'freestyle' %}
  {% assign freestyle = true %}
{% endif %}{% endfor %}
{% if freestyle %}
{% endif %}

If / Else

If else should be well known from any language imaginable. Liquid allows you to write simple expressions in the if.

{% if %}
  Hi {{ }}
{% endif %}

{% if == 'seth' %}
  hi seth
{% endif %}

{% if != 'seth' %} 
  you aren't seth
{% endif %}

{% if == null %}
   no address on file
{% endif %}

{% if invoice.lines == empty %}
   no items have been added to this invoice
{% endif %}

{% if > 0 %}
   you still need to pay this invoice
{% else %}
   thanks for paying this invoice
{% endif %}

For Loops

Liquid allows for loops over collections. This is great in Invoices plugin to loop over things like the line items in an invoice.

{% for item in invoice.lines %} 
  {{ item.description }}
{% endfor %}

During every for loop there are following helper variables available for extra styling needs:

forloop.length   # => length of the entire for loop
forloop.index    # => index of the current iteration 
forloop.index0   # => index of the current iteration (zero based) 
forloop.rindex   # => how many items are still left?
forloop.rindex0  # => how many items are still left? (zero based)
forloop.first    # => is this the first iteration?
forloop.last     # => is this the last iteration?

There are several attributes you can use to influence which items you receive in your loop. limit lets you restrict how many items you get offset lets you start the collection with the nth item.

# array = [1,2,3,4,5,6]
{% for item in array limit:2 offset:2 %} 
  {{ item }}
{% endfor %} 
# results in 3,4

Instead of looping over an existing collection, you can define a range of numbers to loop through. The range can be defined by both literal and variable numbers:

# if item.quantity is 4...
{% for i in (1..item.quantity) %}
  {{ i }}
{% endfor %}
# results in 1,2,3,4
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