From 8ae25a8e41168801590fdb95891cc5990b4db21c Mon Sep 17 00:00:00 2001 From: Jeremy Kemper Date: Sun, 31 Jan 2010 18:13:56 -0800 Subject: Introduce class_attribute to declare inheritable class attributes. Writing an attribute on a subclass behaves just like overriding the superclass reader method. Unifies and replaces most usage of cattr_accessor, class_inheritable_attribute, superclass_delegating_attribute, and extlib_inheritable_attribute. --- .../lib/active_support/core_ext/class/attribute.rb | 36 ++++++++++++++++++++++ 1 file changed, 36 insertions(+) create mode 100644 activesupport/lib/active_support/core_ext/class/attribute.rb (limited to 'activesupport/lib') diff --git a/activesupport/lib/active_support/core_ext/class/attribute.rb b/activesupport/lib/active_support/core_ext/class/attribute.rb new file mode 100644 index 0000000000..d74219cb93 --- /dev/null +++ b/activesupport/lib/active_support/core_ext/class/attribute.rb @@ -0,0 +1,36 @@ +require 'active_support/core_ext/object/metaclass' +require 'active_support/core_ext/module/delegation' + +class Class + # Declare a class-level attribute whose value is inheritable and + # overwritable by subclasses: + # + # class Base + # class_attribute :setting + # end + # + # class Subclass < Base + # end + # + # Base.setting = true + # Subclass.setting # => true + # Subclass.setting = false + # Subclass.setting # => false + # Base.setting # => true + # + # This matches normal Ruby method inheritance: think of writing an attribute + # on a subclass as overriding the reader method. + # + # For convenience, a query method is defined as well: + # + # Subclass.setting? # => false + def class_attribute(*attrs) + attrs.each do |attr| + metaclass.send(:define_method, attr) { } + metaclass.send(:define_method, "#{attr}?") { !!send(attr) } + metaclass.send(:define_method, "#{attr}=") do |value| + metaclass.send(:define_method, attr) { value } + end + end + end +end -- cgit v1.2.3