Accessing model attributes in ActiveSupport::Concern module

Rails
#1

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.

my model:

class Job < ActiveRecord::Base
include ImageModel

image_dir = "jobs"end

my 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
endend

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

#2

On Fri, Sep 20, 2013 at 6:39 AM, Josh J. [email protected]
wrote:

def image_dir
def self.image_dir
@image_dir ||= ‘jobs’
end
end

and access it through the model’s class:

File.open(Rails.root.join(‘public’, ‘images’, self.class.image_dir,
new_image.original_filename), ‘wb’) do |f|

To add a note, if image_dir is persistently stored in the db you can
use the default opt in your Migration.

#3

Felix,

You defined image_dir as a local variable in the scope of the Job class.
It
goes out of scope (and, since nothing else references it, gets cleaned
up)
after the class definition of Job is evaluated. Instead, define
image_dir
on instances of Job:

class Job < ActiveRecord::Base
include ImageModel

def image_dir
@image_dir ||= ‘jobs’
end
end

Better yet, since image_dir is the same for every instance of Job, make
it
a class method:

class Job < ActiveRecord::Base
include ImageModel

def self.image_dir
@image_dir ||= ‘jobs’
end
end

and access it through the model’s class:

File.open(Rails.root.join(‘public’, ‘images’, self.class.image_dir,
new_image.original_filename), ‘wb’) do |f|