Provide read_attribute_for_serialization as the API to serialize attributes.

2 files changed, 26 insertions, 5 deletions

diff --git a/activemodel/lib/active_model/serialization.rb b/activemodel/lib/active_model/serialization.rb
index a756b9f205..7bc3f997b5 100644
--- a/activemodel/lib/active_model/serialization.rb
+++ b/activemodel/lib/active_model/serialization.rb
@@ -78,7 +78,8 @@ module ActiveModel
         attribute_names -= Array.wrap(except).map(&:to_s)
       end
 
-      hash = attributes.slice(*attribute_names)
+      hash = {}
+      attribute_names.each { |n| hash[n] = read_attribute_for_serialization(n) }
 
       method_names = Array.wrap(options[:methods]).select { |n| respond_to?(n) }
       method_names.each { |n| hash[n] = send(n) }
@@ -95,13 +96,33 @@ module ActiveModel
     end
 
     private
+
+      # Hook method defining how an attribute value should be retrieved for
+      # serialization. By default this is assumed to be an instance named after
+      # the attribute. Override this method in subclasses should you need to
+      # retrieve the value for a given attribute differently:
+      #
+      #   class MyClass
+      #     include ActiveModel::Validations
+      #
+      #     def initialize(data = {})
+      #       @data = data
+      #     end
+      #
+      #     def read_attribute_for_serialization(key)
+      #       @data[key]
+      #     end
+      #   end
+      #
+      alias :read_attribute_for_serialization :send
+
       # Add associations specified via the <tt>:include</tt> option.
       #
       # Expects a block that takes as arguments:
       #   +association+ - name of the association
       #   +records+     - the association record(s) to be serialized
       #   +opts+        - options for the association records
-      def serializable_add_includes(options = {})
+      def serializable_add_includes(options = {}) #:nodoc:
         return unless include = options[:include]
 
         unless include.is_a?(Hash)
diff --git a/activemodel/test/cases/serialization_test.rb b/activemodel/test/cases/serialization_test.rb
index 29bcdeae67..1ec915d245 100644
--- a/activemodel/test/cases/serialization_test.rb
+++ b/activemodel/test/cases/serialization_test.rb
@@ -77,12 +77,12 @@ class SerializationTest < ActiveModel::TestCase
     assert_equal expected , @user.serializable_hash(:methods => [:bar])
   end
 
-  def test_should_not_call_methods_for_attributes
-    def @user.name
+  def test_should_use_read_attribute_for_serialization
+    def @user.read_attribute_for_serialization(n)
       "Jon"
     end
 
-    expected = { "name" => "David" }
+    expected = { "name" => "Jon" }
     assert_equal expected, @user.serializable_hash(:only => :name)
   end