extract the instrumentation key to be const and frozen string

Author: yosiat

lib/active_model/default_serializer.rb

@@ -15,7 +15,7 @@ def initialize(object, options={})
     end
 
     def as_json(options={})
-      instrument('!serialize') do
+      instrument do
         return [] if @object.nil? && @wrap_in_array
         hash = @object.as_json
         @wrap_in_array ? [hash] : hash

lib/active_model/serializable.rb

@@ -2,12 +2,14 @@
 
 module ActiveModel
   module Serializable
+    INSTRUMENTATION_KEY = "!serialize.active_model_serializers".freeze
+
     def self.included(base)
       base.extend Utils
     end
 
     def as_json(options={})
-      instrument('!serialize') do
+      instrument do
         if root = options.fetch(:root, json_key)
           hash = { root => serializable_object(options) }
           hash.merge!(serializable_data)
@@ -19,9 +21,7 @@ def as_json(options={})
     end
 
     def serializable_object_with_notification(options={})
-      instrument('!serialize') do
-        serializable_object(options)
-      end
+      instrument { serializable_object(options) }
     end
 
     def serializable_data
@@ -51,9 +51,9 @@ def get_namespace
       modules[0..-2].join('::') if modules.size > 1
     end
 
-    def instrument(action, &block)
+    def instrument(&block)
       payload = { serializer: self.class.name }
-      ActiveSupport::Notifications.instrument("#{action}.active_model_serializers", payload, &block)
+      ActiveSupport::Notifications.instrument(INSTRUMENTATION_KEY, payload, &block)
     end
   end
 end