1 files changed, 107 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/properties.rb b/activerecord/lib/active_record/properties.rb
new file mode 100644
index 0000000000..39c39ad9ff
--- /dev/null
+++ b/activerecord/lib/active_record/properties.rb
@@ -0,0 +1,107 @@
+module ActiveRecord
+  module Properties
+    extend ActiveSupport::Concern
+
+    Type = ConnectionAdapters::Type
+
+    module ClassMethods
+      # Defines or overrides a property on this model. This allows customization of
+      # Active Record's type casting behavior, as well as adding support for user defined
+      # types.
+      #
+      # ==== Examples
+      #
+      # The type detected by Active Record can be overriden.
+      #
+      #   # db/schema.rb
+      #   create_table :store_listings, force: true do |t|
+      #     t.decimal :price_in_cents
+      #   end
+      #
+      #   # app/models/store_listing.rb
+      #   class StoreListing < ActiveRecord::Base
+      #   end
+      #
+      #   store_listing = StoreListing.new(price_in_cents: '10.1')
+      #
+      #   # before
+      #   store_listing.price_in_cents # => BigDecimal.new(10.1)
+      #
+      #   class StoreListing < ActiveRecord::Base
+      #     property :price_in_cents, Type::Integer.new
+      #   end
+      #
+      #   # after
+      #   store_listing.price_in_cents # => 10
+      #
+      # Users may also define their own custom types, as long as they respond to the methods
+      # defined on the value type. The `type_cast` method on your type object will be called
+      # with values both from the database, and from your controllers. See
+      # `ActiveRecord::Properties::Type::Value` for the expected API. It is recommended that your
+      # type objects inherit from an existing type, or the base value type.
+      #
+      #   class MoneyType < ActiveRecord::Type::Integer
+      #     def type_cast(value)
+      #       if value.include?('$')
+      #         price_in_dollars = value.gsub(/\$/, '').to_f
+      #         price_in_dollars * 100
+      #       else
+      #         value.to_i
+      #       end
+      #     end
+      #   end
+      #
+      #   class StoreListing < ActiveRecord::Base
+      #     property :price_in_cents, MoneyType.new
+      #   end
+      #
+      #   store_listing = StoreListing.new(price_in_cents: '$10.00')
+      #   store_listing.price_in_cents # => 1000
+      def property(name, cast_type)
+        name = name.to_s
+        user_provided_columns[name] = ConnectionAdapters::Column.new(name, nil, cast_type)
+      end
+
+      # Returns an array of column objects for the table associated with this class.
+      def columns
+        @columns ||= add_user_provided_columns(connection.schema_cache.columns(table_name)).each do |column|
+          if Type::DecimalWithoutScale === column.cast_type
+            ActiveSupport::Deprecation.warn <<-MESSAGE.strip_heredoc
+              Decimal columns with 0 scale being automatically treated as integers
+              is deprecated, and will be removed in a future version of Rails. If
+              you'd like to keep this behavior, add
+
+                property :#{column.name}, Type::Integer.new
+
+              to your #{name} model.
+            MESSAGE
+          end
+        end
+      end
+
+      # Returns a hash of column objects for the table associated with this class.
+      def columns_hash
+        @columns_hash ||= Hash[columns.map { |c| [c.name, c] }]
+      end
+
+      def reset_column_information # :nodoc:
+        super
+
+        @columns = nil
+        @columns_hash = nil
+      end
+
+      private
+
+      def user_provided_columns
+        @user_provided_columns ||= {}
+      end
+
+      def add_user_provided_columns(schema_columns)
+        schema_columns.reject { |column|
+          user_provided_columns.key? column.name
+        } + user_provided_columns.values
+      end
+    end
+  end
+end