Ruby on Rails : Filter with has_many :through Association

Question

I have a form in my index.html.erb and i would like to filter the projects with the "eligibles" table. How can I do with has_many :through association ? I wrote a request in my controller but it doesn't work.

Thank you very much for your advice !

MODEL: Project_eligible.rb

class ProjectEligible < ApplicationRecord
  belongs_to :project
  belongs_to :eligible
end

project.rb

class Project < ApplicationRecord
  has_many :project_eligibles
  has_many :eligibles, through: :project_eligibles

  scope :eligibles, -> (eligibles) { where eligibles: eligibles }
end

eligible.rb

class Eligible < ApplicationRecord
  has_many :project_eligibles
  has_many :projects, through: :project_eligibles
end

CONTROLLER: project_controller.rb

def index
    @search = Search.new(search_params)
    @eligibles = Eligible.all

    session[:search] = params[:search] if params[:search].present?
    request = Project

    return @projects = request.page(params[:page]).order("expiration ASC").paginate(:page => params[:page], :per_page => 2) unless session[:search].present?

    request = request.joins(:eligibles).where(eligibles: session[:search]['eligibles']) if session[:search]['eligibles'].present?
    @projects = request.page(params[:page]).order("expiration ASC").paginate(:page => params[:page], :per_page => 2)
end

private

def search_params
    if params[:search].present?
        p = params.require(:search).permit!
        session[:search] = p
    else
        session[:search]
    end
end

VIEW: Index.html.erb

<div class="form-inputs" id="form">
    <%= simple_form_for @search, method: :get, url: projects_path do |f| %>
      <div>
          <%= f.input :eligible, :include_blank => "Tous publics", required: false, label: false, collection: @eligibles, class: 'form-control' %>
      </div>
      <div>
          <%= f.submit 'GO', class: 'btn btn-primary paddind-category btn-from-search' %>
      </div>
    <% end %>
</div>

Answer 1

The solution is:

 request = request.joins(:project_eligibles).where(project_eligibles: {eligible_id: session[:search]['eligible']}) if session[:search]['eligible'].present?

And not: request = request.joins(:eligibles).where(eligibles: session[:search]['eligibles']) if session[:search]['eligibles'].present?