Validate attachment format for specific models in Rails 4

Question

I have a polymorphic association with an Attachment model with profiles and documents tables. I have included following code in my attachment.rb:

class Attachment < ActiveRecord::Base
  belongs_to :attachable, polymorphic: true
  has_attached_file :attach,
                    :storage => :s3,
                    :s3_credentials => "#{Rails.root}/config/s3.yml",
                    :url => ":s3_domain_url",
                    :path => "/contents/:id/:basename.:extension"
  validates_attachment_content_type :attach,
                                    :content_type => ['application/msword',
                                                       'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
                                                       'application/pdf',
                                                       'image/jpeg', 'image/jpg', 'image/png']
end

and in my profile.rb

class Profile < ActiveRecord::Base
  has_many :attachments, as: :attachable
  accepts_nested_attributes_for :attachments
end

in my document.rb

class Document < ActiveRecord::Base
      has_many :attachments, as: :attachable
      accepts_nested_attributes_for :attachments
end

My requirement is when I save my profile it will validate only the images format, and when I save documents it will validate only the application format. Please guide me on how to solve this.

Answer 1

attachment.rb

validates_attachment :attach, :presence => true, :with => %r{\.(jpeg|jpg|png)$}i, :if => Proc.new{|f| f.attachable_type == 'Profile' }