refactoring attachment model of learning objects

app/models/learning_object/attachment.rb

 class LearningObject::Attachment
-  attr_accessor :bitstreams
-
-  def initialize(bitstreams)
-    @bitstreams = bitstreams
-  end
-
-  def get_retrievelink
-    get_bitstream_retrievelink_of "ORIGINAL"
-  end
-
-  def get_filename
-    get_bitstream_filename_of "ORIGINAL"
-  end
-
-  private
-
-  def get_bitstream_retrievelink_of name
-    values = @bitstreams.select { |v| v["bundleName"] == name }
-    unless values.empty?
-      return "#{DspaceService.link}#{values.first["retrieveLink"]}"
-    end
-  end
-
-  def get_bitstream_filename_of name
-    values = @bitstreams.select { |v| v["bundleName"] == name }
-    unless values.empty?
-      return values.first["name"]
-    end
-  end
-
+  include ActiveModel::Model
+  attr_accessor :id, :name, :link, :retrieve_link, :description, :format, :mime_type, :size
 end