gecko-dev/xpcom/glue/Observer.h
Mounir Lamouri f354a15e76 Bug 678694 - (5/7) Add a non-XPCOM observer system. sr=cjones
This adding an Observer<T> class and an ObserverList<T> class. The former can
get notifications. The later have an array if Observer<T>s and can Broadcast
notifications to them.
2011-11-02 14:47:32 +01:00

106 lines
3.2 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is Mozilla Foundation
* Portions created by the Initial Developer are Copyright (C) 2011
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Mounir Lamouri <mounir.lamouri@mozilla.com> (Original Author)
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#ifndef mozilla_Observer_h
#define mozilla_Observer_h
#include "nsTArray.h"
namespace mozilla {
/**
* Observer<T> provides a way for a class to observe something.
* When an event has to be broadcasted to all Observer<T>, Notify() method
* is called.
* T represents the type of the object passed in argument to Notify().
*
* @see ObserverList.
*/
template <class T>
class Observer
{
public:
virtual ~Observer() { }
virtual void Notify(const T& aParam) = 0;
};
/**
* ObserverList<T> tracks Observer<T> and can notify them when Broadcast() is
* called.
* T represents the type of the object passed in argument to Broadcast() and
* sent to Observer<T> objects through Notify().
*
* @see Observer.
*/
template <class T>
class ObserverList
{
public:
/**
* Note: When calling AddObserver, it's up to the caller to make sure the
* object isn't going to be release as long as RemoveObserver hasn't been
* called.
*
* @see RemoveObserver()
*/
void AddObserver(Observer<T>* aObserver) {
mObservers.AppendElement(aObserver);
}
void RemoveObserver(Observer<T>* aObserver) {
mObservers.RemoveElement(aObserver);
}
PRUint32 Length() {
return mObservers.Length();
}
void Broadcast(const T& aParam) {
PRUint32 size = mObservers.Length();
for (PRUint32 i=0; i<size; ++i) {
mObservers[i]->Notify(aParam);
}
}
protected:
nsTArray<Observer<T>*> mObservers;
};
} // namespace mozilla
#endif // mozilla_Observer_h