adding routes. catching nulls

app/controllers/api/v1/mobile_controller.rb

@@ -16,6 +16,8 @@ class Api::V1::MobileController < ApplicationController
     if params[:class]
       model = params[:class].classify.constantize
       respond_with model.all.to_json
+    else
+      respond_with nil.to_json
     end
   end
 

config/routes.rb

@@ -94,6 +94,7 @@ Railsgoat::Application.routes.draw do
   namespace :api, defaults: {format: 'json'} do
     namespace :v1 do
         resources :users
+        resources :mobile
     end
    end