Question

I’m trying to set some class variables to store paths in a Rails application (but I think this more a ruby question)

Basically my class looks like this

class Image < ActiveRecord::Base

   @@path_to_folder = "app/assets"
   @@images_folder = "upimages"
   @@path_to_images = File.join(@@path_to_folder, @@images_folder)

end

But when I try to access @@path_to_images from my controller by doing Image.path_to_images, I get a NoMethodError

When I try with Image.class_eval( @@path_to_images ), I get uninitialized class variable @@path_to_images in ImagesController

I’ve searched around and all I’ve seen says those would work, so I’m very confused about this

What’s more, I tried defining simple classes with the ruby console like so

 class Bidule
     @@foo = "foo"
     Bar = "bar"
 end

And so I tried, I think, all the ways possible (previous 2 included) to access them but no way I always get an exception raised

Answer 1

Rails provides class level attribute accessor for this functionality

Try

class Image < ActiveRecord::Base
  cattr_accessor :path_to_folder
  @@path_to_folder = "app/assets"
end

Then to access path_to_folder class variable just use

Image.path_to_folder

But people always suggest to avoid class variables due to its behavior in inheritance.So you can use constants like

class Image < ActiveRecord::Base
   PATH_TO_FOLDER = "app/assets"
end

Then you can access the constant like

Image::PATH_TO_FOLDER