chromium/base/scoped_multi_source_observation.h

// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_SCOPED_MULTI_SOURCE_OBSERVATION_H_
#define BASE_SCOPED_MULTI_SOURCE_OBSERVATION_H_

#include <stddef.h>

#include <vector>

#include "base/check.h"
#include "base/containers/contains.h"
#include "base/memory/raw_ptr.h"
#include "base/ranges/algorithm.h"
#include "base/scoped_observation_traits.h"

namespace base {

// ScopedMultiSourceObservation is used to keep track of plural observation,
// e.g. where an observer observes more than a single source.
//
// Use base::ScopedObservation for objects that observe only a single source.
//
// When ScopedMultiSourceObservation 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:
//     ScopedMultiSourceObservation<Foo, FooObserver> foo_observations_{this};
//   };
//
//   MyFooObserver::OnFooCreated(Foo* foo) {
//     foo_observations_.AddObservation(foo);
//   }
//
////////////////////////////////////////////////////////////////////////////////
//
// By default `ScopedMultiSourceObservation` only works with sources that expose
// `AddObserver` and `RemoveObserver`. However, it's also possible to
// adapt it to custom function names (say `AddFoo` and `RemoveFoo` accordingly)
// by tailoring ScopedObservationTraits<> for the given Source and Observer --
// see `base/scoped_observation_traits.h` for details.
//

template <class Source, class Observer>
class ScopedMultiSourceObservation { … };

}  // namespace base

#endif  // BASE_SCOPED_MULTI_SOURCE_OBSERVATION_H_