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