Rails Lighthouse ticket #1639

observer_on_option.diff

From 9616243694718347d19bcf9b25dbe69260cbb845 Mon Sep 17 00:00:00 2001
From: Gabriel Gironda <gabriel.gironda@gmail.com>
Date: Tue, 27 Jan 2009 16:33:54 -0600
Subject: [PATCH] Adds an :on and :after/:before option to AR observers

---
 activerecord/lib/active_record/observer.rb |   89 ++++++++++++++++++++++------
 activerecord/test/cases/observer_test.rb   |   78 ++++++++++++++++++++++++
 2 files changed, 148 insertions(+), 19 deletions(-)
 create mode 100644 activerecord/test/cases/observer_test.rb

diff --git a/activerecord/lib/active_record/observer.rb b/activerecord/lib/active_record/observer.rb
index b35e407..c16284e 100644
--- a/activerecord/lib/active_record/observer.rb
+++ b/activerecord/lib/active_record/observer.rb
@@ -107,6 +107,21 @@ module ActiveRecord
   #
   # The AuditObserver will now act on both updates to Account and Balance by treating them both as records.
   #
+  # If the audit observer only needs to watch a separate set of observable object updates on each kind of model, the
+  # observed updates can be specified via the :on option to observe
+  #
+  #   class AuditObserver < ActiveRecord::Observer
+  #     observe :account, :after => [:create, :update]
+  #     observe :balance, :on => :after_save
+  #
+  #     def after_update(record)
+  #       AuditTrail.new(record, "UPDATED")
+  #     end
+  #     
+  #     def after_create(record); '...'; end
+  #     def after_save(record); '...'; end
+  #   end
+  #
   # == Available callback methods
   #
   # The observer can implement callback methods for each of the methods described in the Callbacks module.
@@ -141,13 +156,17 @@ module ActiveRecord
   #
   class Observer
     include Singleton
-
+    write_inheritable_hash :observable_updates, {}
+    
     class << self
+      
       # Attaches the observer to the supplied model classes.
       def observe(*models)
-        models.flatten!
-        models.collect! { |model| model.is_a?(Symbol) ? model.to_s.camelize.constantize : model }
-        define_method(:observed_classes) { Set.new(models) }
+        options = models.extract_options!
+        set_watch_options(models, options)
+        models = constantize_models(models)
+        already_observed = read_inheritable_attribute(:observed_classes)
+        write_inheritable_attribute(:observed_classes, Set.new(Array(already_observed)) + Set.new(models))
       end
 
       # The class observed by default is inferred from the observer's class name:
@@ -159,6 +178,28 @@ module ActiveRecord
           nil
         end
       end
+    
+    private
+
+      def set_watch_options(models, options)
+        on_methods = options.inject([]) do |methods,(key,val)|
+          if [:before, :after].include?(key)
+            methods.concat(Array(val).map {|v| :"#{key}_#{v}"})
+          elsif key == :on
+            methods.concat(Array(val).map(&:to_sym))
+          end
+          methods
+        end
+        constantize_models(models).each do |model|
+          existing = (obs = read_inheritable_attribute(:observable_updates)) ? obs[model] : []
+          write_inheritable_hash(:observable_updates, model => Array(existing) + on_methods)
+        end
+      end
+      
+      def constantize_models(models)
+        models.flatten.collect { |model| model.is_a?(Symbol) ? model.to_s.camelize.constantize : model }
+      end
+      
     end
 
     # Start observing the declared classes and their subclasses.
@@ -168,7 +209,7 @@ module ActiveRecord
 
     # Send observed_method(object) if the method exists.
     def update(observed_method, object) #:nodoc:
-      send(observed_method, object) if respond_to?(observed_method)
+      send(observed_method, object) if listening_for?(object, observed_method)
     end
 
     # Special method sent by the observed class when it is inherited.
@@ -177,21 +218,31 @@ module ActiveRecord
       self.class.observe(observed_classes + [subclass])
       add_observer!(subclass)
     end
+    
+    def observed_classes
+      self.class.read_inheritable_attribute(:observed_classes) || Set.new([self.class.observed_class].compact.flatten)
+    end
+    
+  protected
+    
+    def listening_for?(object, observed_method)
+      respond_to?(observed_method) && watching?(object, observed_method)
+    end
+      
+    def watching?(object, observed_method)
+      observed = self.class.read_inheritable_attribute(:observable_updates)
+      observed[object.class].blank? || observed[object.class].include?(observed_method.to_sym)
+    end
+    
+    def observed_subclasses
+      observed_classes.sum([]) { |klass| klass.send(:subclasses) }
+    end
 
-    protected
-      def observed_classes
-        Set.new([self.class.observed_class].compact.flatten)
-      end
-
-      def observed_subclasses
-        observed_classes.sum([]) { |klass| klass.send(:subclasses) }
-      end
-
-      def add_observer!(klass)
-        klass.add_observer(self)
-        if respond_to?(:after_find) && !klass.method_defined?(:after_find)
-          klass.class_eval 'def after_find() end'
-        end
+    def add_observer!(klass)
+      klass.add_observer(self)
+      if respond_to?(:after_find) && !klass.method_defined?(:after_find)
+        klass.class_eval 'def after_find() end'
       end
+    end
   end
 end
diff --git a/activerecord/test/cases/observer_test.rb b/activerecord/test/cases/observer_test.rb
new file mode 100644
index 0000000..515b7fe
--- /dev/null
+++ b/activerecord/test/cases/observer_test.rb
@@ -0,0 +1,78 @@
+require "cases/helper"
+require 'models/topic'
+require 'models/developer'
+require 'models/reply'
+
+class ActivityObserver < ActiveRecord::Observer
+  observe :topic, :after => [:create, :destroy], :before => :update
+  observe :topic, :developer, :on => [:before_destroy, 'before_save']
+  observe :reply
+end
+
+class ObserverTest < ActiveRecord::TestCase
+  
+  def setup
+    @observer = ActivityObserver.instance
+  end
+  
+  lambda do # with topic 
+    topic = Topic.new
+    
+    test "should observe after_create on Topic" do
+      @observer.expects(:after_create).with(topic)
+      topic.send(:notify, :after_create)
+    end
+
+    test "should observe after_destroy on Topic" do
+      @observer.expects(:after_destroy).with(topic)
+      topic.send(:notify, :after_destroy)
+    end
+    
+    test "should observe before_update on Topic" do
+      @observer.expects(:before_update).with(topic)
+      topic.send(:notify, :before_update)
+    end
+    
+    test "should observe before_destroy on Topic" do 
+      @observer.expects(:before_destroy).with(topic)
+      topic.send(:notify, :before_destroy)
+    end
+  
+    test "should observe before_save on Topic" do
+      @observer.expects(:before_save).with(topic)
+      topic.send(:notify, :before_save)
+    end
+  
+    test "should ignore after_save and after_validation on topic" do
+      @observer.expects(:after_save).with(topic).never
+      @observer.expects(:after_validation).with(topic).never
+      topic.send(:notify, :after_save)
+      topic.send(:notify, :after_validation)
+    end
+    
+  end.call
+
+  lambda do # with developer
+    developer = Developer.new
+    
+    test "should observe before_destroy on Developer" do
+      @observer.expects(:before_destroy).with(developer)
+      developer.send(:notify, :before_destroy)
+    end
+  
+    test "should observe before_save on Developer" do
+      @observer.expects(:before_save).with(developer)
+      developer.send(:notify, :before_save)
+    end
+    
+  end.call
+  
+  test "should observe all callbacks on Reply" do
+    reply = Reply.new
+    ActiveRecord::Callbacks::CALLBACKS.each do |callback|
+      @observer.expects(callback).with(reply)
+      reply.send(:notify, callback)
+    end
+  end
+  
+end
-- 
1.6.0.5