Simplifies observer implementation [#6065 state:resolved]

activerecord/lib/active_record/observer.rb

@@ -89,51 +89,29 @@ module ActiveRecord
   # singletons and that call instantiates and registers them.
   #
   class Observer < ActiveModel::Observer
-    class_attribute :observed_methods
-    self.observed_methods = [].freeze
 
     def initialize
       super
       observed_descendants.each { |klass| add_observer!(klass) }
     end
 
-    def self.method_added(method)
-      method = method.to_sym
-
-      if ActiveRecord::Callbacks::CALLBACKS.include?(method)
-        self.observed_methods += [method]
-        self.observed_methods.freeze
-      end
-    end
-
     protected
 
       def observed_descendants
         observed_classes.sum([]) { |klass| klass.descendants }
       end
 
-      def observe_callbacks?
-        self.class.observed_methods.any?
-      end
-
       def add_observer!(klass)
         super
-        define_callbacks klass if observe_callbacks?
+        define_callbacks klass
       end
 
       def define_callbacks(klass)
-        existing_methods = klass.instance_methods.map { |m| m.to_sym }
         observer = self
-        observer_name = observer.class.name.underscore.gsub('/', '__')
 
-        self.class.observed_methods.each do |method|
-          callback = :"_notify_#{observer_name}_for_#{method}"
-          unless existing_methods.include? callback
-            klass.send(:define_method, callback) do  # def _notify_user_observer_for_before_save
-              observer.update(method, self)          #   observer.update(:before_save, self)
-            end                                      # end
-            klass.send(method, callback)             # before_save :_notify_user_observer_for_before_save
-          end
+        ActiveRecord::Callbacks::CALLBACKS.each do |callback|
+          next unless respond_to?(callback)
+          klass.send(callback){|record| observer.send(callback, record)}
         end
       end
   end

activerecord/test/cases/lifecycle_test.rb

@@ -9,10 +9,19 @@ class SpecialDeveloper < Developer; end
 
 class SalaryChecker < ActiveRecord::Observer
   observe :special_developer
+  attr_accessor :last_saved
 
   def before_save(developer)
     return developer.salary > 80000
   end
+
+  module Implementation
+    def after_save(developer)
+      self.last_saved = developer
+    end
+  end
+  include Implementation
+
 end
 
 class TopicaAuditor < ActiveRecord::Observer
@@ -179,4 +188,11 @@ class LifecycleTest < ActiveRecord::TestCase
     developer = SpecialDeveloper.new :name => 'Rookie', :salary => 50000
     assert !developer.save, "allowed to save a developer with too low salary"
   end
+
+  test "able to call methods defined with included module" do # https://rails.lighthouseapp.com/projects/8994/tickets/6065-activerecordobserver-is-not-aware-of-method-added-by-including-modules
+    SalaryChecker.instance # activate
+    developer = SpecialDeveloper.create! :name => 'Roger', :salary => 100000
+    assert_equal developer, SalaryChecker.instance.last_saved
+  end
+
 end