Getting root key from AR::Relation

lib/active_model/serializer/array_serializer.rb

@@ -7,6 +7,7 @@ module ActiveModel
       attr_reader :meta, :meta_key
 
       def initialize(objects, options = {})
+        @resource = objects
         @objects  = objects.map do |object|
           serializer_class = options.fetch(
             :serializer,
@@ -19,7 +20,11 @@ module ActiveModel
       end
 
       def json_key
-        @objects.first.json_key.pluralize if @objects.first
+        if @objects.first
+          @objects.first.json_key.pluralize
+        else
+          @resource.name.downcase.pluralize if @resource.try(:name)
+        end
       end
 
       def root=(root)