update AR::AttributeMethods::BeforeTypeCast docs [ci skip]

activerecord/lib/active_record/attribute_methods/before_type_cast.rb

@@ -7,11 +7,29 @@ module BeforeTypeCast
         attribute_method_suffix "_before_type_cast"
       end
 
+      # Returns the value of the attribuet identified by +attr_name+ before
+      # typecasting and deserialization.
+      #
+      #   class Task < ActiveRecord::Base
+      #   end
+      #
+      #   task = Task.new(id: '1', completed_on: '2012-10-21')
+      #   task.read_attribute('id')                            # => 1
+      #   task.read_attribute_before_type_cast('id')           # => '1'
+      #   task.read_attribute('completed_on')                  # => Sun, 21 Oct 2012
+      #   task.read_attribute_before_type_cast('completed_on') # => "2012-10-21"
       def read_attribute_before_type_cast(attr_name)
         @attributes[attr_name]
       end
 
       # Returns a hash of attributes before typecasting and deserialization.
+      #
+      #   class Task < ActiveRecord::Base
+      #   end
+      #
+      #   task = Task.new(title: nil, is_done: true, completed_on: '2012-10-21')
+      #   task.attributes_before_type_cast
+      #   # => {"id"=>nil, "title"=>nil, "is_done"=>true, "completed_on"=>"2012-10-21", "created_at"=>nil, "updated_at"=>nil}
       def attributes_before_type_cast
         @attributes
       end