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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef mozilla_Observer_h
#define mozilla_Observer_h
#include "nsTObserverArray.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() = default;
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.AppendElementUnlessExists(aObserver);
}
/**
* Remove the observer from the observer list.
* @return Whether the observer has been found in the list.
*/
bool RemoveObserver(Observer<T>* aObserver) {
return mObservers.RemoveElement(aObserver);
}
uint32_t Length() { return mObservers.Length(); }
/**
* Call Notify() on each item in the list.
*/
void Broadcast(const T& aParam) {
for (Observer<T>* obs : mObservers.ForwardRange()) {
obs->Notify(aParam);
}
}
protected:
nsTObserverArray<Observer<T>*> mObservers;
};
} // namespace mozilla
#endif // mozilla_Observer_h
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