Rails - Sep 2013 - Accessing model attributes in ActiveSupport::Concern module

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

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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|

On Wednesday, September 18, 2013 9:11:59 AM UTC-4, Felix Gläske
wrote:
>
> 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
>
>
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On Fri, Sep 20, 2013 at 6:39 AM, Josh Jordan
<josh.jordan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> 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|
To add a note, if image_dir is persistently stored in the db you can
use the default opt in your Migration.

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