Grouping posts by user in has_many through relation collection with Rails 5

Question

I'm trying to display Users (devise) in a collection (has_many through).

    <%= @collection.posts.count %> designs by
    <% @collection.posts.each do |post| %>
      <%= link_to image_tag(post.designer.avatar.url.to_s, class: "avatar-small"), post.designer %>
    <% end %>

but it displaying duplicates as in

I need to group by designer.id. So I added @collection_designers line but I could not manage to group by designer id.🤷‍♂️

class CollectionsController < ApplicationController

  def show
    @collection = Collection.find(params[:id])

    #I need to group for designer.id I guess but I could not manage it
    @collection_designers = Collection.find(params[:id]).groups(designers.id) 
  end

  ...

---

Relations:

models/collection.rb

class Collection < ApplicationRecord
  belongs_to :designer
  has_many :collectivizations
  has_many :posts, through: :collectivizations
end

models/collectivization.rb

class Collectivization < ApplicationRecord
    belongs_to :post
    belongs_to :collection
end

models/post.rb

class Post < ApplicationRecord
  belongs_to :category
  belongs_to :designer
  has_many :collectivizations
  has_many :collections, through: :collectivizations

Answer 1

You need to find uniq designers ids at first

designer_ids = @collection.posts.distinct.pluck(:designer_id)

And after it find designers by these ids

@designers = Designer.where(id: designer_ids)