83 lines
1.9 KiB
C++
83 lines
1.9 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_Observer_h
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#define mozilla_Observer_h
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#include "nsTObserverArray.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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{
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mObservers.AppendElementUnlessExists(aObserver);
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}
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/**
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* Remove the observer from the observer list.
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* @return Whether the observer has been found in the list.
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*/
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bool RemoveObserver(Observer<T>* aObserver)
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{
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return mObservers.RemoveElement(aObserver);
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}
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uint32_t Length()
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{
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return mObservers.Length();
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}
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void Broadcast(const T& aParam)
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{
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typename nsTObserverArray<Observer<T>*>::ForwardIterator iter(mObservers);
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while (iter.HasMore()) {
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Observer<T>* obs = iter.GetNext();
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obs->Notify(aParam);
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}
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}
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protected:
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nsTObserverArray<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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