Accessing model attributes in ActiveSupport::Concern module

Question

I have some models which share the same functionality just on other paths. So I decided to put these methods in a module and set the path in the model. My problem is that I'm not able to access the attribute in my module.

model:

class Job < ActiveRecord::Base
  include ImageModel

  image_dir = "jobs"
end

module:

module ImageModel
  extend ActiveSupport::Concern

  def delete_image
      unless pic_link == "" || pic_link == nil
        begin
          if File.delete(Rails.root.join("public", "images", image_dir, pic_link))
            return true
          else
            return false
          end
        rescue
          return true #an error occured but when the image does not exist we still return true
        end
      end

      return true
    end

    def replace_image(new_image)
      File.open(Rails.root.join("public", "images", image_dir, new_image.original_filename), "wb") do |f|
        if f.write new_image.read
          delete_image
          pic_link = new_image.original_filename
          return true #everything went fine
        else
          return false #return false if new image could not be written
        end
      end
    end
end

The error i get:

undefined local variable or method `image_dir' for #<Job:0x007f8a93b9e8d8>

on this line:

File.open(Rails.root.join("public", "images", image_dir, new_image.original_filename), "wb") do |f|

Did I miss something or did I oversee something important?

Felix

Answer 1

I think the design of module still have room to improve. But for this specific question, here is the quickfix.

class Job < ActiveRecord::Base
  include ImageModel

  def image_dir
    "jobs"
  end
end