1 files changed, 29 insertions, 1 deletions
diff --git a/activemodel/lib/active_model/serializer.rb b/activemodel/lib/active_model/serializer.rb
index 6e89eec09c..99a007de31 100644
--- a/activemodel/lib/active_model/serializer.rb
+++ b/activemodel/lib/active_model/serializer.rb
@@ -18,12 +18,25 @@ module ActiveModel
             serializer.new(item, scope).serializable_hash
           end
         end
+
+        def serialize_ids(collection, scope)
+          # use named scopes if they are present
+          return collection.ids if collection.respond_to?(:ids)
+
+          collection.map do |item|
+            item.read_attribute_for_serialization(:id)
+          end
+        end
       end
 
       class HasOne < Config
         def serialize(object, scope)
           serializer.new(object, scope).serializable_hash
         end
+
+        def serialize_ids(object, scope)
+          object.read_attribute_for_serialization(:id)
+        end
       end
     end
 
@@ -80,7 +93,11 @@ module ActiveModel
     end
 
     def serializable_hash
-      hash = attributes
+      attributes.merge(associations)
+    end
+
+    def associations
+      hash = {}
 
       _associations.each do |association|
         associated_object = send(association.name)
@@ -90,6 +107,17 @@ module ActiveModel
       hash
     end
 
+    def association_ids
+      hash = {}
+
+      _associations.each do |association|
+        associated_object = send(association.name)
+        hash[association.name] = association.serialize_ids(associated_object, scope)
+      end
+
+      hash
+    end
+
     def attributes
       hash = {}