refactor to make way for easy feature adding

lib/active_model/serializer/adapter/json.rb

@@ -6,37 +6,16 @@ class Adapter
       class Json < Adapter
         def serializable_hash(options = nil)
           options ||= {}
+
           if serializer.respond_to?(:each)
-            @result = serializer.map { |s| FlattenJson.new(s).serializable_hash(options) }
+            @result = serialize_array_without_root(serializer, options)
           else
             @hash = {}
 
-            @core = cache_check(serializer) do
-              serializer.attributes(options)
-            end
+            @core = resource_object_for(serializer, options)
+
+            add_resource_relationships(serializer)
 
-            serializer.associations.each do |association|
-              serializer = association.serializer
-              opts = association.options
-
-              if serializer.respond_to?(:each)
-                array_serializer = serializer
-                @hash[association.key] = array_serializer.map do |item|
-                  cache_check(item) do
-                    item.attributes(opts)
-                  end
-                end
-              else
-                @hash[association.key] =
-                  if serializer && serializer.object
-                    cache_check(serializer) do
-                      serializer.attributes(options)
-                    end
-                  elsif opts[:virtual_value]
-                    opts[:virtual_value]
-                  end
-              end
-            end
             @result = @core.merge @hash
           end
 
@@ -47,6 +26,61 @@ def fragment_cache(cached_hash, non_cached_hash)
           Json::FragmentCache.new().fragment_cache(cached_hash, non_cached_hash)
         end
 
+        private
+
+        # iterate through the associations on the serializer,
+        # adding them to @hash as needed (as singular or plural)
+        def add_resource_relationships(serializer)
+          serializer.associations.each do |association|
+            serializer = association.serializer
+            opts = association.options
+
+            if serializer.respond_to?(:each)
+              add_has_many_relationship(association.key, serializer, opts)
+            else
+              add_singular_relationship(association.key, serializer, opts)
+            end
+          end
+
+          @hash
+        end
+
+        # add a singular relationship
+        def add_singular_relationship(key, serializer, options)
+          @hash[key] = serialized_or_virtual_of(serializer, options)
+        end
+
+        # add a many relationship
+        def add_has_many_relationship(key, serializer, options)
+          @hash[key] = serialize_array(serializer, options)
+        end
+
+        def serialize_array_without_root(serializer, options)
+          serializer.map { |s| FlattenJson.new(s).serializable_hash(options) }
+        end
+
+        # a virtual value is something that doesn't need a serializer,
+        # such as a ruby array, or any other raw value
+        def serialized_or_virtual_of(serializer, options)
+          if serializer && serializer.object
+            resource_object_for(serializer, options)
+          elsif options[:virtual_value]
+            options[:virtual_value]
+          end
+        end
+
+        def serialize_array(serializer, options)
+          serializer.map do |item|
+            resource_object_for(item, options)
+          end
+        end
+
+        def resource_object_for(item, options)
+          cache_check(item) do
+            item.attributes(options)
+          end
+        end
+
       end
     end
   end