Accessing model attributes in ActiveSupport::Concern module - ruby-on-rails

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

Answer 2

You should define your image_dir = "jobs" in the module itself. because you are including your module in your model, and your module is not able to get the declaration, you have done in your model.
Or you can change your delete_image method to take parameters :
def delete_image(image_dir)
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
and where you are calling that method, pass an argument like this:
delete_image("jobs")
same in the case of replace_image method:
def replace_image(new_image, image_dir)
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
Hope it will help. Thanks