ClassAttr

Adds #class_attr_accessor (and reader/writer) and #inheritable_class_attr_accessor (and reader/writer of course) to Class.

class Polygon
  class_attr_accessor :sides
end

Polygon.sides = 5
Polygon.sides #=> 5

class Square < Polygon
end

Square.sides #=> nil


class InheritablePolygon
  inheritable_class_attr_accessor :sides
end

Polygon.sides = 4

class NewSquare < Polygon
end

Square.sides #=> 4

You can provide default values using a hash with :default set for the last value, or if just creating one accessor/reader/writer add => defaultvalue to the end, this example should make it more clear:

class Person
  class_attr_accessor :name => 'John Doe'
  inheritable_class_attr_accessor :arms, :legs, :default => 2
  inheritable_class_attr_accessor :fingers, :toes, :default => 5
end

class Agent < Person
  @name = "James Bond"
end  

Person.name #=> "John Doe"
Person.arms #=> 2
Person.toes #=> 5
Agent.name  #=> "James Bond"
Agent.legs  #=> 2

Install

(sudo) gem install class_attr

Use

require 'class_attr'

Thanks

• http://railstips.org/blog/archives/2006/11/18/class-and-instance-variables-in-ruby/ For originally demystifying the class instance variable thing.
• http://www.raulparolari.com/Rails/class_inheritable For ideas on how to implement class level attribute accessors which inherit values.

Copyright

Copyright (c) 2010 Joshua Hawxwell. See LICENSE for details.