gistfile1.txt

- form_for @demo, :html => { :multipart => true } do |f| 
  = f.error_messages 
  %p
    = f.label :name
    %br
    = f.text_field :name
  - f.fields_for :images do |builder|
    %p
      - if builder.object.new_record?
        = builder.label :image, "Image"
        = builder.file_field :image
      - else
        = image_tag f.demo.image.url(:thumb) # ???
      - unless builder.object.new_record?
        = builder.check_box :_destroy
        = builder.label :_destroy, "Remove"
  %p
    = submit_tag