gistfile1.rb

# How to use Paperclip for generic attachment types on models in Ruby on Rails

class User < ActiveRecord::Base
  has_many :user_assets
end

# example of building a model which is a generic attachment asset
@user.build_user_asset(:asset_type => "podcast", :attached_file => some_uploaded_file_data)

# make a generic asset class, with instances initialized for specific asset
# types through Paperclip

# models/user_asset.rb
class UserAsset < ActiveRecord::Base
  belongs_to :users
  attr_accessor :attached_file

  def setup_attached
    opts         = ASSETS[asset_type.to_sym].dup
    opts[:path]  = ":rails_root/public"+opts[:url]
    less_than    = opts.delete :less_than
    content_type = opts.delete :content_type

    self.class.has_attached_file :asset, opts
    if less_than
      self.class.validates_attachment_size :asset, :less_than => less_than
    end
    if content_type
      self.class.validates_attachment_content_type :asset, :content_type => content_type
    end
    # reach into paperclip, make it setup the attachment at run-time 
    self.asset.assign(@attached_file) if @attached_file
  end

  def after_initialize
    if !asset_type.nil?
      setup_attached
    else
      raise <<-TXT
        Error: UserAsset asset_type is nil, paperclip cannot lookup
        ASSET[asset_type]. You forgot to pass :asset_type param to UserAsset
        new() or build() ?
      TXT
    end
  end
end


# config/initializers/user_asset.rb
# Unify the Paperclip options for attachments instead of duplicating them
# throughout the models code

ASSET_IMAGE_CONTENT_TYPES = ['image/jpg', 'image/jpeg', 'image/gif', 'image/png', 'image/x-png', 'image/pjpeg']

ASSET_VIDEO_CONTENT_TYPES = [ "audio/mpeg","audio/mpg", "audio/x-mpeg", "audio/mp3","audio/x-mp3","audio/mpeg3","audio/x-mpeg3","audio/x-mpg","audio/x-mpegaudio","video/mp4","video/x-mp4","video/mv4","video/x-mv4","video/m4v","video/x-m4v"]

ASSET_AUDIO_CONTENT_TYPES = ["audio/mpeg","audio/mpg", "audio/x-mpeg", "audio/mp3","audio/x-mp3","audio/mpeg3","audio/x-mpeg3","audio/x-mpg","audio/x-mpegaudio","video/mp4","video/x-mp4","video/mv4","video/x-mv4","video/m4v","video/x-m4v"]

# use the same directory/file structure for all attachments: 0000/0000/file.style.ext
ASSET_INTERPOLATION = ":partition/:basename:.style.:extension"

DEFAULT_IMAGE_ATTACHMENT = {
  :less_than      => 2.megabytes,
  :default_style  => :original,
  :styles         => {:original => "300x600", :thumb => "150x300"},
  :content_type   => ASSET_IMAGE_CONTENT_TYPES,
  :url            => "/assets/profile_images/"+ASSET_INTERPOLATION
}

CORP_IMAGE_ATTACHMENT = {
  :less_than      => 4.megabytes,
  :default_style  => :medium,
  :styles         => {:small => "100x100", :medium => "200x200", :large => "300x300"},
  :content_type   => ASSET_IMAGE_CONTENT_TYPES,
  :url            => "/assets/corps/items/"+ASSET_INTERPOLATION
}

DEFAULT_PODCAST_ATTACHMENT = {
  :less_than      => 25.megabytes,
  :content_type   => ASSET_AUDIO_CONTENT_TYPES,
  :url            => "/assets/podcasts/"+ASSET_INTERPOLATION
}

ASSETS = {
  :media     => {:less_than => 100.megabytes,
                 :url => "/assets/corps/media/"+ASSET_INTERPOLATION},
                 #no content_type, any type can be uploaded

  :podcast   => {:less_than => 100.megabytes,
                 :url => "/assets/users/podcasts/"+ASSET_INTERPOLATION,
                 :content_type => ASSET_AUDIO_CONTENT_TYPES},

  :logo      => CORP_IMAGE_ATTACHMENT.merge({:less_than => 5.megabytes,
                                             :url => "/assets/corps/logos/"+ASSET_INTERPOLATION}),
}

## Global paperclip interpolations used by all models having Paperclip attachments

Paperclip::Attachment.interpolations[:partition] = proc do |attachment, style|
  ("%08d" % attachment.instance.id).scan(/\d{4}/).join("/").to_s
end