query object example

controller.rb

def index
  @posts = PublishedQuery.new(self, Post).published
end

query_object.rb

class PublishedQuery
  def initialize(controller, model)
    @controller = controller
    @model      = model
  end

  def criteria
    @model.criteria
  end

  def published
    @controller.user_signed_in? ? criteria.all : criteria.published
  end
end

query_object_spec.rb

require "spec_helper"

describe PublishedQuery do
  let(:controller) { mock(PostsController) }
  let(:model) { Post }
  subject { PublishedQuery.new(controller, model) }

  describe ".criteria" do
    it "returns a model criteria" do
      expect(subject.criteria).to eq(model.criteria)
    end
  end

  describe ".published" do
    context "when user is logged in" do
      before do
        controller.stub(:user_signed_in?) { true }
      end

      it "returns criteria 'all'" do
        expect(subject.published).to eq(model.all)
      end
    end

    context "when user is not logged in" do
      before do
        controller.stub(:user_signed_in?) { false }
      end

      it "returns criteria 'published'" do
        expect(subject.published).to eq(model.published)
      end
    end
  end
end