accepts_nested_attributes_for not saving paperclip image

I am trying to save images through nested model

**model:

Listing 
    has_many:photos
    accepts_nested_attributes_for :photos, :allow_destroy => true

Photo 
    belongs_to:listing
   has_attached_file :data, :styles=>{:featured => "88x63#", :search_result => "122x91#"}

listings controller:

def new
    @listing = Listing.new
    @listing.photos.build
    respond_to do |format|
      format.html # new.html.erb
      format.xml  { render :xml => @listing }
    end
  end

 def create
   开发者_如何学运维 @listing = Listing.new(params[:listing])
    if @listing.save
      redirect_to(:action=>'index')
    else
      render :action => "new"
    end
end

view:

  <%= form_for [@listing] do |f| %>
   <%= f.fields_for :photos do |ph| %>
      <%= ph.file_field :data %>
   <% end%>
<%end%>

Here I mentioned only one field in the view, but I used lot of fields and all are saved in the database except the data (image) field.

If I validate the presence of data in the Photo model I got "photo should not be empty" message though I uploaded a image.

You won't be able to upload images unless you have a multi-part form Add :html => { :multipart => true } declaration to the form_for declaration so you get something like this

<%= form_for(@listing, :html => { :multipart => true }) do |f| %>