Liquid filter for Ruby arrays with Jekyll

Question

I want to write a Jekyll filter, which take a list as a argument, and return a string of a list without redundent elements.

My filter code is:

module Jekyll
    module ArrayToSet
        def array_to_set_string(arr)
            arr.uniq.to_s
        end
    end
end

Liquid::Template.register_filter(Jekyll::ArrayToSet)

The usage code is

{{ [1,2,2,3] | array_to_set_string }}

But the complilation jekyll build failed, because the arr in the function is nul.

When I change the input argument as string "[1,2,2,3]" , arr is a normal string.

Does jekyll forbid non-string argument for filter?

Answer 1

Liquid doesn't accept Ruby code like that, but it can work with Ruby objects once they have been created by some other means (a filter or a tag).

So either make a method that creates an array, or accept strings and convert them to arrays before processing.

Example of using a two-step process to create an array and then process:

module Filter
  def to_array(str)
    str.split(',')
  end

  def uniq(arr)
    arr.uniq
  end
end

>> {{ '1,2,2,3' | to_array | uniq }}
1 2 3

You could also roll it all into one method of course:

module Filter
  def to_array_uniq(str)
    str.split(',').uniq
  end
end