What's the proper way to initialize a class_attribute in Rails?

Question

What's the proper way to initialize a class_attribute in Rails?

I am using this:

class Foo < ActiveRecord::Base

  class_attribute :foobar
  self.foobar = []

  # ...

end

Which seems to work fine, but also seems to look a bit non-Railsy to me.

Answer 1

Everything is described here: http://apidock.com/rails/Class/class_attribute

If you click on "Show source" you will see there are no options available to set default value. You are doing it right.

Answer 2

A default option was added on branch master of Rails this year, check: https://github.com/rails/rails/pull/29270. With this change, you can do:

class Foo < ActiveRecord::Base
  class_attribute :foobar, default: []
end

Answer 3

What you've done works well (unless you are inheriting).

If you are inheriting from this class you can use the inherited method to avoid 'leaking'.

def self.inherited(sub_class)
  self.foobar = self.foobar.clone
  # or `self.foobar = []`
end