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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_SCOPED_OBSERVER_H_
#define BASE_SCOPED_OBSERVER_H_
#include <stddef.h>
#include <algorithm>
#include <vector>
#include "base/logging.h"
#include "base/macros.h"
#include "base/stl_util.h"
// ScopedObserver is used to keep track of the set of sources an object has
// attached itself to as an observer. When ScopedObserver is destroyed it
// removes the object as an observer from all sources it has been added to.
// Basic example (as a member variable):
//
// class MyFooObserver : public FooObserver {
// ...
// private:
// ScopedObserver<Foo, FooObserver> observed_foo_{this};
// };
//
// For cases with methods not named AddObserver/RemoveObserver:
//
// class MyFooStateObserver : public FooStateObserver {
// ...
// private:
// ScopedObserver<Foo,
// FooStateObserver,
// &Foo::AddStateObserver,
// &Foo::RemoveStateObserver>
// observed_foo_{this};
// };
template <class Source,
class Observer,
void (Source::*AddObsFn)(Observer*) = &Source::AddObserver,
void (Source::*RemoveObsFn)(Observer*) = &Source::RemoveObserver>
class ScopedObserver {
public:
explicit ScopedObserver(Observer* observer) : observer_(observer) {}
~ScopedObserver() {
RemoveAll();
}
// Adds the object passed to the constructor as an observer on |source|.
void Add(Source* source) {
sources_.push_back(source);
(source->*AddObsFn)(observer_);
}
// Remove the object passed to the constructor as an observer from |source|.
void Remove(Source* source) {
auto it = std::find(sources_.begin(), sources_.end(), source);
DCHECK(it != sources_.end());
sources_.erase(it);
(source->*RemoveObsFn)(observer_);
}
void RemoveAll() {
for (size_t i = 0; i < sources_.size(); ++i)
(sources_[i]->*RemoveObsFn)(observer_);
sources_.clear();
}
bool IsObserving(Source* source) const {
return base::Contains(sources_, source);
}
bool IsObservingSources() const { return !sources_.empty(); }
size_t GetSourcesCount() const { return sources_.size(); }
private:
Observer* observer_;
std::vector<Source*> sources_;
DISALLOW_COPY_AND_ASSIGN(ScopedObserver);
};
#endif // BASE_SCOPED_OBSERVER_H_
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