Question

I am using attachment model as polymorphic association. How to change path and url parameters based on the associations.

Attachment Model

class Attachment < ActiveRecord::Base
  belongs_to :user
  belongs_to :attachable, :polymorphic => true

  has_attached_file :attachment,
                    :url  => "/attachments/:id/:basename.:extension",
                    :path => ":rails_root/public/attachments/:id/:basename.:extension",
                    :default_url => "/attachments/original/no-file.txt"
end

Project Model

class Project < ActiveRecord::Base
 ...
 has_many :attachments, :as => :attachable, :dependent => :destroy
end

Client

class Client < ActiveRecord::Base
 ...
 has_many :attachments, :as => :attachable, :dependent => :destroy
end

following path files are saving fine.

:path => ":rails_root/public/attachments/:id/:basename.:extension",

but I need to save files based on association like, for this how do pass the parameters to ‘path’. ‘attachable_type’ defines the which association upload file belongs

/attachments/project/
/attachments/client/

Answer 1

You can use Paperclip Interpolations. Interpolations allows you to call a method to determine the value of a part of the path.

class Attachment < ActiveRecord::Base
  belongs_to :user
  belongs_to :attachable, :polymorphic => true

  Paperclip.interpolates :attached_to do |attachment, style|
    attachment.instance.attachable.class.to_s.downcase
  end

  has_attached_file :attachment,
                    :url  => "/attachments/:id/:basename.:extension",
                    :path => ":rails_root/public/attachments/:attached_to/:id/:basename.:extension",
                    :default_url => "/attachments/original/no-file.txt"
end