1 files changed, 43 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/attribute_methods/before_type_cast.rb b/activerecord/lib/active_record/attribute_methods/before_type_cast.rb
index d4f529acbf..faee99ccd1 100644
--- a/activerecord/lib/active_record/attribute_methods/before_type_cast.rb
+++ b/activerecord/lib/active_record/attribute_methods/before_type_cast.rb
@@ -1,5 +1,28 @@
 module ActiveRecord
   module AttributeMethods
+    # = Active Record Attribute Methods Before Type Cast
+    #
+    # <tt>ActiveRecord::AttributeMethods::BeforeTypeCast</tt> provides a way to
+    # read the value of the attributes before typecasting and deserialization.
+    #
+    #   class Task < ActiveRecord::Base
+    #   end
+    #
+    #   task = Task.new(id: '1', completed_on: '2012-10-21')
+    #   task.id           # => 1
+    #   task.completed_on # => Sun, 21 Oct 2012
+    #
+    #   task.attributes_before_type_cast
+    #   # => {"id"=>"1", "completed_on"=>"2012-10-21", ... }
+    #   task.read_attribute_before_type_cast('id')           # => 1
+    #   task.read_attribute_before_type_cast('completed_on') # => "2012-10-21"
+    #
+    # In addition to #read_attribute_before_type_cast and #attributes_before_type_cast,
+    # it declares a method for all attributes with the <tt>*_before_type_cast</tt>
+    # suffix.
+    #
+    #   task.id_before_type_cast           # => "1"
+    #   task.completed_on_before_type_cast # => "2012-10-21"
     module BeforeTypeCast
       extend ActiveSupport::Concern
 
@@ -7,11 +30,31 @@ module ActiveRecord
         attribute_method_suffix "_before_type_cast"
       end
 
+      # Returns the value of the attribute 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
+      #   # => {"id"=>nil, "title"=>nil, "is_done"=>true, "completed_on"=>Sun, 21 Oct 2012, "created_at"=>nil, "updated_at"=>nil}
+      #   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