put layout object as embeded obj in design. have bug with solving uploading file

app/models/design.rb

@@ -11,7 +11,7 @@ class Design
   validates_presence_of :title
   validates_presence_of :author
 
-  mount_uploader :layout, DesignFileUploader
+  embeds_one :layout
   mount_uploader :structure_css, DesignFileUploader
 
   embeds_many :themes

app/models/layout.rb

@@ -2,7 +2,7 @@ class Layout < DesignFile
    
   embedded_in :design
 
-
+  attr_reader :content
   field :name, :index => true
   references_many :children, :class_name => "Item"
   has_many :layout_parts
@@ -11,6 +11,9 @@ class Layout < DesignFile
   validates_format_of :name, :with => /^[0-9a-zA-Z\-_]+$/
   validates_uniqueness_of :name
 
+  def content
+    self.file.read
+  end
   def self.exist_one?
     Layout.count > 0
   end

app/views/admin/designs/_form.html.erb

@@ -18,7 +18,7 @@
 <p>
 <%= f.label "layout", t('admin.layout') %>
 <%  if @design.layout.blank? %>
-    <%= f.file_field :layout %>
+    <%= f.file_field :layout_file %>
   <% else%>
     <%= File.basename (Design.all.last.layout.url)  %>
 <% end %>