title: How to use two controllers with one model in Rails
body: <p>I have an Order model. Customers interact with the Order model through an Orders controller. Admins interact with the Order model through a Purchases controller.</p>
  
  <p>Mostly it's working, except this happens:</p>
  
  <ol>
  <li>An admin user goes to new_purchase_path</li>
  <li>The app uses the "create" action in the purchases controller, as
      expected</li>
  <li>The app then uses the "new" action in the order controller (not the
  purchases controller)</li>
  <li>App then renders the "app/purchases/new" view (not the
  "app/orders/new" view), despite the fact that it has switched to using the orders controller</li>
  <li>After the admin creates the order, the app then renders the
  "app/orders/show" view using the orders controller</li>
  </ol>
  
  <p>What I really need to happen is this:</p>
  
  <ol>
  <li>An admin users goes to new_purchase_path</li>
  <li>The app then uses the "create" action in the purchases controller</li>
  <li>The app then uses the "new" action in the purchases controller</li>
  <li>The app then renders the "app/purchases/new" view</li>
  <li>After the admin creates the order, the app then renders the
  "app/purchases/show" view using the purchases controller</li>
  </ol>
  
  <p>In app/controllers/purchases_controller.rb I have this:</p>
  
  <pre><code>  def new
      @purchase = Order.new
      respond_with @purchase
    end
  </code></pre>
  
  <p>If have tried variations like...</p>
  
  <pre><code>  def new
      @purchase = Order.new
      respond_with @purchase, :controller =&gt; :purchases
    end
  </code></pre>
  
  <p>...but nothing like that is documented for respond_with, and naturally it doesn't work. What can I do?</p>