rails 3 polymorphic association with paperclip and multiple models - ruby-on-rails

Question

I want to make polymorphic associations with paperclip, and allow my user to have one avatar and multiple images.
Attachment model:
class Attachment < ActiveRecord::Base
belongs_to :attachable, :polymorphic => true
end
class Avatar < Attachment
has_attached_file :image, :styles => { :thumb => "150x150>", :view => "260x180>" },
end
class Image < Attachment
has_attached_file :image, :styles => { :thumb => "150x150>", :view => "260x180>" },
end
User Model:
has_one :avatar, :as => :attachable, :class_name => 'Attachment', :conditions => {:type => 'avatar'}
accepts_nested_attributes_for :avatar
User Controller:
def edit
#user.build_avatar
end
User View form:
<%= form_for #user, :html => { :multipart => true } do |f| %>
<%= f.fields_for :avatar do |asset| %>
<% if asset.object.new_record? %>
<%= asset.file_field :image %>
<% end %>
<% end %>
when I attempt to save the changes I get the error => unknown attribute: avatar
if I remove the :class_name => 'attachment' in the has_one association I get the error =>
uninitialized constant User::Avatar
I need to also attach avatars to blog posts, so I need the association to be polymorphic (or atleast i think so)
I am stumped and any help would be greatly appreciated.

Answer 1

I do have a project in the works that is successfully using Paperclip and polymorphic associations. Let me show you what I have, and maybe you can apply it to your project:
class Song < ActiveRecord::Base
...
has_one :artwork, :as => :artable, :dependent => :destroy
accepts_nested_attributes_for :artwork
...
end
class Album < ActiveRecord::Base
...
has_one :artwork, :as => :artable, :dependent => :destroy
accepts_nested_attributes_for :artwork
...
end
class Artwork < ActiveRecord::Base
belongs_to :artable, :polymorphic => true
attr_accessible :artwork_content_type, :artwork_file_name, :artwork_file_size, :artwork
# Paperclip
has_attached_file :artwork,
:styles => {
:small => "100",
:full => "400"
}
validates_attachment_content_type :artwork, :content_type => 'image/jpeg'
end
the songs form and the albums form include this as a partial:
<div class="field">
<%= f.fields_for :artwork do |artwork_fields| %>
<%= artwork_fields.label :artwork %><br />
<%= artwork_fields.file_field :artwork %>
<% end %>
don't forget to include :html => { :multipart => true } with the form
artworks_controller.rb
class ArtworksController < ApplicationController
def create
#artwork = Artwork.new(params[:artwork])
if #artwork.save
redirect_to #artwork.artable, notice: 'Artwork was successfully created.'
else
redirect_to #artwork.artable, notice: 'An error ocurred.'
end
end
end
and finally, an excerpt from songs_controller.rb:
def new
#song = Song.new
#song.build_artwork
end

Answer 2

I'm not sure you really need to be polymorphic. How about this approach, which uses has_many :through? In plain English, the user has one avatar which has multiple images, and through this association you can call User.images to get the collection of images associated with the avatar.
http://guides.rubyonrails.org/association_basics.html
class User < ActiveRecord::Base
has_one :avatar
has_many :images, :through => :avatar
end
class Avatar < ActiveRecord::Base
belongs_to :user
has_many :images
end
class Image < ActiveRecord::Base
belongs_to :avatar
has_attached_file :image, :styles => { :thumb => "150x150>", :view => "260x180>" },
end
Having said all of this, I am left to wonder why you need to go through all this anyway. Why not just do
class User < ActiveRecord::Base
has_many :avatars
end
which would give you as many images (avatars) as you want.