acts_as_list on has_many :through and sortablejs

Question

I have a fairly large question that I've been unable to resolve after a full day of reading articles, documentation and other Stack questions. At this point it's just messing with my mind!

I have an app that is Vue/Vuetify on the frontend with a data-table that I want to be able to reorder with sortablejs. On the backend, I have a Rails API that I'd like to use the acts_as_list gem to handle reordering for me.

Ideally I'd be able to call something like Category.first.items.last.move_higher, however because I have a join model I'm having to put acts_as_list and the position column on the join model instead of the Item model. Is there a better way to arrange this?

category.rb

class Category < ApplicationRecord
  has_many :categories_items
  has_many :items, through: :categories_items, source: :item

  accepts_nested_attributes_for :items

end

item.rb

class Item < ApplicationRecord
  has_many :categories_items
  has_many :categories, through: :categories_items, source: :category

end

categories_item.rb

class CategoriesItem < ApplicationRecord
  belongs_to :category
  belongs_to :item

  acts_as_list scope: :category
end

Answer 1

With that structure you'll definitely need to reorder by calling methods on the join model. You can however use the Rails delegate class method to delegate reordering methods to the join model if you like:

https://api.rubyonrails.org/classes/Module.html#method-i-delegate

All of this assumes that you need items and categories to have a has_and_belongs_to_many type relationship.