What is the proper way to access class variables in Ruby 1.9?

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