michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef mozilla_Observer_h
michael@0: #define mozilla_Observer_h
michael@0: 
michael@0: #include "nsTArray.h"
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: /**
michael@0:  * Observer<T> provides a way for a class to observe something.
michael@0:  * When an event has to be broadcasted to all Observer<T>, Notify() method
michael@0:  * is called.
michael@0:  * T represents the type of the object passed in argument to Notify().
michael@0:  *
michael@0:  * @see ObserverList.
michael@0:  */
michael@0: template <class T>
michael@0: class Observer
michael@0: {
michael@0: public:
michael@0:   virtual ~Observer() { }
michael@0:   virtual void Notify(const T& aParam) = 0;
michael@0: };
michael@0: 
michael@0: /**
michael@0:  * ObserverList<T> tracks Observer<T> and can notify them when Broadcast() is
michael@0:  * called.
michael@0:  * T represents the type of the object passed in argument to Broadcast() and
michael@0:  * sent to Observer<T> objects through Notify().
michael@0:  *
michael@0:  * @see Observer.
michael@0:  */
michael@0: template <class T>
michael@0: class ObserverList
michael@0: {
michael@0: public:
michael@0:   /**
michael@0:    * Note: When calling AddObserver, it's up to the caller to make sure the
michael@0:    * object isn't going to be release as long as RemoveObserver hasn't been
michael@0:    * called.
michael@0:    *
michael@0:    * @see RemoveObserver()
michael@0:    */
michael@0:   void AddObserver(Observer<T>* aObserver) {
michael@0:     mObservers.AppendElement(aObserver);
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Remove the observer from the observer list.
michael@0:    * @return Whether the observer has been found in the list.
michael@0:    */
michael@0:   bool RemoveObserver(Observer<T>* aObserver) {
michael@0:     return mObservers.RemoveElement(aObserver);
michael@0:   }
michael@0: 
michael@0:   uint32_t Length() {
michael@0:     return mObservers.Length();
michael@0:   }
michael@0: 
michael@0:   void Broadcast(const T& aParam) {
michael@0:     uint32_t size = mObservers.Length();
michael@0:     for (uint32_t i=0; i<size; ++i) {
michael@0:       mObservers[i]->Notify(aParam);
michael@0:     }
michael@0:   }
michael@0: 
michael@0: protected:
michael@0:   nsTArray<Observer<T>*> mObservers;
michael@0: };
michael@0: 
michael@0: } // namespace mozilla
michael@0: 
michael@0: #endif // mozilla_Observer_h