Added `decorator_class` class and instance methods

lib/draper/model_support.rb

@@ -2,16 +2,24 @@ module Draper::ModelSupport
   extend ActiveSupport::Concern
 
   def decorator(options = {})
-    @decorator ||= "#{self.class.name}Decorator".constantize.decorate(self, options.merge(:infer => false))
+    @decorator ||= decorator_class.decorate(self, options.merge(:infer => false))
     block_given? ? yield(@decorator) : @decorator
   end
 
+  def decorator_class
+    "#{self.class.name}Decorator".constantize
+  end
+
   alias :decorate :decorator
 
   module ClassMethods
     def decorate(options = {})
-      decorator_proxy = "#{model_name}Decorator".constantize.decorate(self.scoped, options)
+      decorator_proxy = decorator_class.decorate(self.scoped, options)
       block_given? ? yield(decorator_proxy) : decorator_proxy
     end
+
+    def decorator_class
+      "#{model_name}Decorator".constantize
+    end
   end
-end
+end