Implement has_one's and serialize_ids

lib/active_model/serializer/associations.rb

@@ -0,0 +1,43 @@
+module ActiveModel
+  class Serializer
+    class Association
+      def initialize(name, options={})
+        @name          = name
+        @options       = options
+
+        self.embed = options[:embed]
+        @embed_key = options[:embed_key] || :id
+        @include   = options[:include]
+
+        serializer = @options[:serializer]
+        @serializer_class = serializer.is_a?(String) ? serializer.constantize : serializer
+      end
+
+      attr_reader :name, :embed_ids, :embed_objects, :embed_key, :include
+      alias embed_ids? embed_ids
+      alias embed_objects? embed_objects
+      alias include? include
+
+      def embed=(embed)
+        @embed_ids     = embed == :id || embed == :ids
+        @embed_objects = embed == :object || embed == :objects
+      end
+
+      def build_serializer(object)
+        @serializer_class ||= Serializer.serializer_for(object)
+
+        if @serializer_class
+          @serializer_class.new(object, @options)
+        else
+          object
+        end
+      end
+
+      class HasOne < Association
+        def key
+          "#{name}_id"
+        end
+      end
+    end
+  end
+end