Added update action

app/controllers/quantities_controller.rb

@@ -39,6 +39,14 @@ class QuantitiesController < ApplicationController
     render :index
   end
 
+  def update
+    if @quantity.update(quantity_params)
+      flash[:notice] = 'Updated quantity'
+    end
+    prepare_quantities
+    render :index
+  end
+
   def destroy
     if @quantity.destroy
       flash[:notice] = 'Deleted quantity'

app/views/quantities/_index.html.erb

@@ -61,7 +61,9 @@
             <%= delete_link quantity_path(q), {remote: true, data: {}} %>
           </td>
         </tr>
-        <% next unless (action_name == "edit") && (q == @quantity) %>
+        <% next unless (q == @quantity) &&
+          ((action_name == "edit") || (action_name == "update" && @quantity.errors.present?))
+        %>
         <tr>
           <td class="form" colspan="6">
             <div id="edit-quantity">