Fixes undefined helper_method for rails 5 api

- [x] rails 5 ActionController::API does not have `helper_method`
anymore

closes #163

lib/decent_exposure/exposure.rb

@@ -67,6 +67,8 @@ def expose_attribute!
     end
 
     def expose_helper_methods!
+      return unless controller.respond_to?(:helper_method)
+
       controller.helper_method attribute.getter_method_name
     end
 

spec/features/api_birds_controller_spec.rb

@@ -0,0 +1,90 @@
+require "spec_helper"
+require "support/rails_app"
+require "rspec/rails"
+
+RSpec.describe Api::BirdsController, type: :controller do
+  let(:bird){ Bird.new }
+
+  context 'when birds relation is exposed' do
+    class Api::BirdsController < API_SUPER_CLASS
+      expose :birds, ->{ Bird.all }
+
+      def index
+        head :ok
+      end
+    end
+
+    it "fetches all birds" do
+      expect(Bird).to receive(:all).and_return([bird])
+      get :index
+      expect(controller.birds).to eq([bird])
+    end
+  end
+
+  context 'when a bird is exposed' do
+    class Api::BirdsController < API_SUPER_CLASS
+      expose :bird
+
+      def show
+        head :ok
+      end
+
+      def new
+        head :ok
+      end
+    end
+
+    it "finds model by id" do
+      expect(Bird).to receive(:find).with("bird-id").and_return(bird)
+      get :show, request_params(id: "bird-id")
+      expect(controller.bird).to eq(bird)
+    end
+
+    it "finds model by bird_id" do
+      expect(Bird).to receive(:find).with("bird-id").and_return(bird)
+      get :new, request_params(bird_id: "bird-id")
+      expect(controller.bird).to eq(bird)
+    end
+
+    it "builds bird if id is not provided" do
+      get :new
+      expect(controller.bird).to be_a(Bird)
+    end
+  end
+
+  context "when bird_params is defined" do
+    class Api::BirdsController < API_SUPER_CLASS
+      expose :bird
+
+      def create
+        head :ok
+      end
+
+      def bird_params
+        params.require(:bird).permit(:name)
+      end
+    end
+
+    it "bird is build with params set" do
+      post :create, request_params(bird: { name: "crow" })
+      expect(controller.bird.name).to eq("crow")
+    end
+  end
+
+  context 'when a bird? with a question mark is exposed' do
+    class Api::BirdsController < API_SUPER_CLASS
+      expose :bird
+      expose :bird?, -> { bird.present? }
+
+      def show
+        head :ok
+      end
+    end
+
+    it "exposes bird?" do
+      expect(Bird).to receive(:find).with("bird-id").and_return(bird)
+      get :show, request_params(id: "bird-id")
+      expect(controller.bird?).to be true
+    end
+  end
+end

spec/support/rails_app.rb

@@ -16,6 +16,10 @@ def routes
       @routes ||= ActionDispatch::Routing::RouteSet.new.tap do |routes|
         routes.draw do
           resources :birds
+
+          namespace :api do
+            resources :birds
+          end
         end
       end
     end
@@ -41,3 +45,15 @@ class ApplicationController < ActionController::Base
 
 class BirdsController < ApplicationController
 end
+
+module Api
+end
+
+API_SUPER_CLASS = if Rails::VERSION::MAJOR < 5
+                    ApplicationController
+                  else
+                    ActionController::API
+                  end
+
+class Api::BirdsController < API_SUPER_CLASS
+end