Listing unique data from liquid objects - ruby-on-rails

Question

I need to be able take a list of objects in liquid and display them on the page in a specific format.
If I have an array of objects (pages), I need to be able to print them in the following way:
list category names (page.category.name)
list each subcategory name with a list of pages under each subcategory name (page.subcategory.name and page.title)
Typically in ruby I would simply group the pages but I can't do that in liquid. The other thing I tried was to capture unique lists of categories and subcategories for pages but I couldn't find a way to get a unique list of items from an array. Any suggest help would be great.

Answer 1

I'm a little late to answer your question, but maybe this will help someone else struggling with the same problem. It's a bit hacky, as Liquid logic tends to be, but it works (at least for me, on Shopify).
Assuming you have a 'pages' array that looks like this:
pages = [
{ name: 'Page 1', category: { name: 'pants' } },
{ name: 'Page 2', category: { name: 'pants' } },
{ name: 'Page 3', category: { name: 'shoes' } },
{ name: 'Page 4', category: { name: 'shirts' } },
{ name: 'Page 5', category: { name: 'shoes' } }
]
This code will return only unique category names:
{% assign delimiter = "," %}
{% assign names_str = "" %}
{% assign names = pages | map: 'category' | map: 'name' %}
{% for name in names %}
{% assign names_arr = names_str | split: delimiter %}
{% unless names_arr contains name %}
{% assign names_str = names_str | append: delimiter | append: name %}
{% endunless %}
{% endfor %}
{% assign names_uniq = names_str | remove_first: delimiter | split: delimiter %}
Result:
names_uniq => [ 'pants', 'shoes', 'shirts' ]