1 files changed, 104 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/observer_array.rb b/activemodel/lib/active_model/observer_array.rb
new file mode 100644
index 0000000000..ab7f86007f
--- /dev/null
+++ b/activemodel/lib/active_model/observer_array.rb
@@ -0,0 +1,104 @@
+require 'set'
+
+module ActiveModel
+  # Stores the enabled/disabled state of individual observers for
+  # a particular model classes.
+  class ObserverArray < Array
+    attr_reader :model_class
+    def initialize(model_class, *args)
+      @model_class = model_class
+      super(*args)
+    end
+
+    def disabled_for?(observer)
+      disabled_observers.include?(observer.class)
+    end
+
+    def disable(*observers, &block)
+      set_enablement(false, observers, &block)
+    end
+
+    def enable(*observers, &block)
+      set_enablement(true, observers, &block)
+    end
+
+    protected
+
+      def disabled_observers
+        @disabled_observers ||= Set.new
+      end
+
+      def observer_class_for(observer)
+        return observer if observer.is_a?(Class)
+
+        if observer.respond_to?(:to_sym) # string/symbol
+          observer.to_s.camelize.constantize
+        else
+          raise ArgumentError, "#{observer} was not a class or a " +
+            "lowercase, underscored class name as expected."
+        end
+      end
+
+      def start_transaction
+        disabled_observer_stack.push(disabled_observers.dup)
+        each_subclass_array do |array|
+          array.start_transaction
+        end
+      end
+
+      def disabled_observer_stack
+        @disabled_observer_stack ||= []
+      end
+
+      def end_transaction
+        @disabled_observers = disabled_observer_stack.pop
+        each_subclass_array do |array|
+          array.end_transaction
+        end
+      end
+
+      def transaction
+        start_transaction
+
+        begin
+          yield
+        ensure
+          end_transaction
+        end
+      end
+
+      def each_subclass_array
+        model_class.descendants.each do |subclass|
+          yield subclass.observers
+        end
+      end
+
+      def set_enablement(enabled, observers)
+        if block_given?
+          transaction do
+            set_enablement(enabled, observers)
+            yield
+          end
+        else
+          observers = ActiveModel::Observer.descendants if observers == [:all]
+          observers.each do |obs|
+            klass = observer_class_for(obs)
+
+            unless klass < ActiveModel::Observer
+              raise ArgumentError.new("#{obs} does not refer to a valid observer")
+            end
+
+            if enabled
+              disabled_observers.delete(klass)
+            else
+              disabled_observers << klass
+            end
+          end
+
+          each_subclass_array do |array|
+            array.set_enablement(enabled, observers)
+          end
+        end
+      end
+  end
+end