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f354a15e76
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.
106 lines
3.2 KiB
C++
106 lines
3.2 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is mozilla.org code.
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*
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* The Initial Developer of the Original Code is Mozilla Foundation
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* Portions created by the Initial Developer are Copyright (C) 2011
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Mounir Lamouri <mounir.lamouri@mozilla.com> (Original Author)
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either of the GNU General Public License Version 2 or later (the "GPL"),
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* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#ifndef mozilla_Observer_h
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#define mozilla_Observer_h
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#include "nsTArray.h"
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namespace mozilla {
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/**
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* Observer<T> provides a way for a class to observe something.
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* When an event has to be broadcasted to all Observer<T>, Notify() method
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* is called.
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* T represents the type of the object passed in argument to Notify().
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*
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* @see ObserverList.
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*/
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template <class T>
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class Observer
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{
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public:
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virtual ~Observer() { }
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virtual void Notify(const T& aParam) = 0;
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};
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/**
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* ObserverList<T> tracks Observer<T> and can notify them when Broadcast() is
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* called.
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* T represents the type of the object passed in argument to Broadcast() and
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* sent to Observer<T> objects through Notify().
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*
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* @see Observer.
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*/
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template <class T>
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class ObserverList
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{
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public:
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/**
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* Note: When calling AddObserver, it's up to the caller to make sure the
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* object isn't going to be release as long as RemoveObserver hasn't been
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* called.
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*
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* @see RemoveObserver()
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*/
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void AddObserver(Observer<T>* aObserver) {
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mObservers.AppendElement(aObserver);
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}
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void RemoveObserver(Observer<T>* aObserver) {
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mObservers.RemoveElement(aObserver);
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}
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PRUint32 Length() {
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return mObservers.Length();
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}
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void Broadcast(const T& aParam) {
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PRUint32 size = mObservers.Length();
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for (PRUint32 i=0; i<size; ++i) {
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mObservers[i]->Notify(aParam);
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}
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}
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protected:
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nsTArray<Observer<T>*> mObservers;
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};
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} // namespace mozilla
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#endif // mozilla_Observer_h
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