1 files changed, 134 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/configuration.rb b/activemodel/lib/active_model/configuration.rb
new file mode 100644
index 0000000000..1757c12ebf
--- /dev/null
+++ b/activemodel/lib/active_model/configuration.rb
@@ -0,0 +1,134 @@
+require 'active_support/concern'
+require 'active_support/core_ext/class/attribute'
+require 'active_support/core_ext/class/attribute_accessors'
+
+module ActiveModel
+  # This API is for Rails' internal use and is not currently considered 'public', so
+  # it may change in the future without warning.
+  #
+  # It creates configuration attributes that can be inherited from a module down
+  # to a class that includes the module. E.g.
+  #
+  #   module MyModel
+  #     extend ActiveModel::Configuration
+  #     config_attribute :awesome
+  #     self.awesome = true
+  #   end
+  #
+  #   class Post
+  #     include MyModel
+  #   end
+  #
+  #   Post.awesome # => true
+  #
+  #   Post.awesome = false
+  #   Post.awesome    # => false
+  #   MyModel.awesome # => true
+  #
+  # We assume that the module will have a ClassMethods submodule containing methods
+  # to be transferred to the including class' singleton class.
+  #
+  # Config options can also be defined directly on a class:
+  #
+  #   class Post
+  #     extend ActiveModel::Configuration
+  #     config_attribute :awesome
+  #   end
+  #
+  # So this allows us to define a module that doesn't care about whether it is being
+  # included in a class or a module:
+  #
+  #   module Awesomeness
+  #     extend ActiveSupport::Concern
+  #
+  #     included do
+  #       extend ActiveModel::Configuration
+  #       config_attribute :awesome
+  #       self.awesome = true
+  #     end
+  #   end
+  #
+  #   class Post
+  #     include Awesomeness
+  #   end
+  #
+  #   module AwesomeModel
+  #     include Awesomeness
+  #   end
+  module Configuration #:nodoc:
+    def config_attribute(name, options = {})
+      klass = self.is_a?(Class) ? ClassAttribute : ModuleAttribute
+      klass.new(self, name, options).define
+    end
+
+    class Attribute
+      attr_reader :host, :name, :options
+
+      def initialize(host, name, options)
+        @host, @name, @options = host, name, options
+      end
+
+      def instance_writer?
+        options.fetch(:instance_writer, false)
+      end
+    end
+
+    class ClassAttribute < Attribute
+      def define
+        if options[:global]
+          host.cattr_accessor name, :instance_writer => instance_writer?
+        else
+          host.class_attribute name, :instance_writer => instance_writer?
+        end
+      end
+    end
+
+    class ModuleAttribute < Attribute
+      def class_methods
+        @class_methods ||= begin
+          if host.const_defined?(:ClassMethods, false)
+            host.const_get(:ClassMethods)
+          else
+            host.const_set(:ClassMethods, Module.new)
+          end
+        end
+      end
+
+      def define
+        host.singleton_class.class_eval <<-CODE, __FILE__, __LINE__
+          attr_accessor :#{name}
+          def #{name}?; !!#{name}; end
+        CODE
+
+        name, host = self.name, self.host
+
+        class_methods.class_eval do
+          define_method(name) { host.send(name) }
+          define_method("#{name}?") { !!send(name) }
+        end
+
+        host.class_eval <<-CODE
+          def #{name};  defined?(@#{name}) ? @#{name} : self.class.#{name}; end
+          def #{name}?; !!#{name}; end
+        CODE
+
+        if options[:global]
+          class_methods.class_eval do
+            define_method("#{name}=") { |val| host.send("#{name}=", val) }
+          end
+        else
+          class_methods.class_eval <<-CODE, __FILE__, __LINE__
+            def #{name}=(val)
+              singleton_class.class_eval do
+                remove_possible_method(:#{name})
+                define_method(:#{name}) { val }
+              end
+            end
+          CODE
+        end
+
+        host.send(:attr_writer, name) if instance_writer?
+      end
+    end
+  end
+end