Enable conditional default_url for Paperclip, to set default url with some method in the model

Readme

In some cases you need to set the default_url of paper clip base on some condition. e.g. You want to set default image on basis of gender of user. For this purpose this gist can make it possible to use a method as default_url. Just copy paper_clip_default_url_fix.rb to initializers folder, and use default_url as mentioned in model.rb

model.rb

class User < ActiveRecord::Base

  def set_picture_respect_to_gender
     self.gender? ? '/images/male.jpg' : '/images/female.jpg'
  end
  
  has_attached_file :display_picture, 
    :styles => { :medium => "150x150>", :thumb => "100x100>", :small => "50x50>" },
    :url => "/system/user/:id/:attachment/:style/:basename.:extension"
    :default_url => :set_picture_respect_to_gender
end

paper_clip_default_url_fix.rb

module Paperclip
  module Interpolations
    def self.interpolate pattern, *args
      if pattern.kind_of? Symbol
        args.first.instance.send(pattern)
      else
        all.reverse.inject( pattern.dup ) do |result, tag|
          result.gsub(/:#{tag}/) do |match|
            send( tag, *args )
          end
        end
      end
    end
  end
end

I know it's outdated as hell, but if anyone is still here - BE CAREFUL WITH THIS CODE! It slows down the code A LOT, especially if you need to get many image urls on the same page.

@AvaelKross Yes its about 8 year old code and I am not sure if its valid any more. But for clarity reasons can you pin-point exactly what code slows down? It slows down the startup or a request cycle?