1 files changed, 116 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/attribute_methods/read.rb b/activerecord/lib/active_record/attribute_methods/read.rb
new file mode 100644
index 0000000000..bea332ef26
--- /dev/null
+++ b/activerecord/lib/active_record/attribute_methods/read.rb
@@ -0,0 +1,116 @@
+module ActiveRecord
+  module AttributeMethods
+    module Read
+      extend ActiveSupport::Concern
+
+      ATTRIBUTE_TYPES_CACHED_BY_DEFAULT = [:datetime, :timestamp, :time, :date]
+
+      included do
+        attribute_method_suffix ""
+
+        cattr_accessor :attribute_types_cached_by_default, :instance_writer => false
+        self.attribute_types_cached_by_default = ATTRIBUTE_TYPES_CACHED_BY_DEFAULT
+
+        # Undefine id so it can be used as an attribute name
+        undef_method :id
+      end
+
+      module ClassMethods
+        # +cache_attributes+ allows you to declare which converted attribute values should
+        # be cached. Usually caching only pays off for attributes with expensive conversion
+        # methods, like time related columns (e.g. +created_at+, +updated_at+).
+        def cache_attributes(*attribute_names)
+          attribute_names.each {|attr| cached_attributes << attr.to_s}
+        end
+
+        # Returns the attributes which are cached. By default time related columns
+        # with datatype <tt>:datetime, :timestamp, :time, :date</tt> are cached.
+        def cached_attributes
+          @cached_attributes ||=
+            columns.select{|c| attribute_types_cached_by_default.include?(c.type)}.map{|col| col.name}.to_set
+        end
+
+        # Returns +true+ if the provided attribute is being cached.
+        def cache_attribute?(attr_name)
+          cached_attributes.include?(attr_name)
+        end
+
+        protected
+          def define_attribute_method(attr_name)
+            if self.serialized_attributes[attr_name]
+              define_read_method_for_serialized_attribute(attr_name)
+            else
+              define_read_method(attr_name.to_sym, attr_name, columns_hash[attr_name])
+            end
+
+            if attr_name == primary_key && attr_name != "id"
+              define_read_method(:id, attr_name, columns_hash[attr_name])
+            end
+          end
+
+        private
+          # Define read method for serialized attribute.
+          def define_read_method_for_serialized_attribute(attr_name)
+            evaluate_attribute_method "def #{attr_name}; unserialize_attribute('#{attr_name}'); end", attr_name
+          end
+
+          # Define an attribute reader method.  Cope with nil column.
+          def define_read_method(symbol, attr_name, column)
+            cast_code = column.type_cast_code('v') if column
+            access_code = cast_code ? "(v=@attributes['#{attr_name}']) && #{cast_code}" : "@attributes['#{attr_name}']"
+
+            unless attr_name.to_s == self.primary_key.to_s
+              access_code = access_code.insert(0, "missing_attribute('#{attr_name}', caller) unless @attributes.has_key?('#{attr_name}'); ")
+            end
+
+            if cache_attribute?(attr_name)
+              access_code = "@attributes_cache['#{attr_name}'] ||= (#{access_code})"
+            end
+            evaluate_attribute_method "def #{symbol}; #{access_code}; end", symbol
+          end
+      end
+
+      # Returns the value of the attribute identified by <tt>attr_name</tt> after it has been typecast (for example,
+      # "2004-12-12" in a data column is cast to a date object, like Date.new(2004, 12, 12)).
+      def read_attribute(attr_name)
+        attr_name = attr_name.to_s
+        attr_name = self.class.primary_key if attr_name == 'id'
+        if !(value = @attributes[attr_name]).nil?
+          if column = column_for_attribute(attr_name)
+            if unserializable_attribute?(attr_name, column)
+              unserialize_attribute(attr_name)
+            else
+              column.type_cast(value)
+            end
+          else
+            value
+          end
+        else
+          nil
+        end
+      end
+
+      # Returns true if the attribute is of a text column and marked for serialization.
+      def unserializable_attribute?(attr_name, column)
+        column.text? && self.class.serialized_attributes[attr_name]
+      end
+
+      # Returns the unserialized object of the attribute.
+      def unserialize_attribute(attr_name)
+        unserialized_object = object_from_yaml(@attributes[attr_name])
+
+        if unserialized_object.is_a?(self.class.serialized_attributes[attr_name]) || unserialized_object.nil?
+          @attributes.frozen? ? unserialized_object : @attributes[attr_name] = unserialized_object
+        else
+          raise SerializationTypeMismatch,
+            "#{attr_name} was supposed to be a #{self.class.serialized_attributes[attr_name]}, but was a #{unserialized_object.class.to_s}"
+        end
+      end
+
+      private
+        def attribute(attribute_name)
+          read_attribute(attribute_name)
+        end
+    end
+  end
+end