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chromium / chromium / src / lkgr / . / base / scoped_multi_source_observation.h
blob: e440f592ff6737e073e9028b7da465fac812231e [file] [log] [blame]
Avi Drissmane4622aa2022-09-08 20:36:06[diff] [blame]1// Copyright 2020 The Chromium Authors
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef BASE_SCOPED_MULTI_SOURCE_OBSERVATION_H_
6#define BASE_SCOPED_MULTI_SOURCE_OBSERVATION_H_
7
8#include <stddef.h>
9
Peter Kasting025a94252025-01-29 21:28:37[diff] [blame]10#include <algorithm>
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]11#include <vector>
12
13#include "base/check.h"
Jan Wilken Dörrieb5a41c32020-12-09 18:55:47[diff] [blame]14#include "base/containers/contains.h"
Keishi Hattori0e45c022021-11-27 09:25:52[diff] [blame]15#include "base/memory/raw_ptr.h"
Andrew Rayskiy799ce712022-11-04 22:42:53[diff] [blame]16#include "base/scoped_observation_traits.h"
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]17
18namespace base {
19
Sigurdur Asgeirsson11031652020-11-12 17:44:25[diff] [blame]20// ScopedMultiSourceObservation is used to keep track of plural observation,
21// e.g. where an observer observes more than a single source.
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]22//
Sigurdur Asgeirsson11031652020-11-12 17:44:25[diff] [blame]23// Use base::ScopedObservation for objects that observe only a single source.
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]24//
Sigurdur Asgeirsson11031652020-11-12 17:44:25[diff] [blame]25// When ScopedMultiSourceObservation is destroyed, it removes the object as an
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]26// observer from all sources it has been added to.
27// Basic example (as a member variable):
28//
29// class MyFooObserver : public FooObserver {
30// ...
31// private:
Sigurdur Asgeirsson11031652020-11-12 17:44:25[diff] [blame]32// ScopedMultiSourceObservation<Foo, FooObserver> foo_observations_{this};
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]33// };
34//
Sigurdur Asgeirsson11031652020-11-12 17:44:25[diff] [blame]35// MyFooObserver::OnFooCreated(Foo* foo) {
36// foo_observations_.AddObservation(foo);
37// }
38//
Andrew Rayskiy799ce712022-11-04 22:42:53[diff] [blame]39////////////////////////////////////////////////////////////////////////////////
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]40//
Andrew Rayskiy799ce712022-11-04 22:42:53[diff] [blame]41// By default `ScopedMultiSourceObservation` only works with sources that expose
42// `AddObserver` and `RemoveObserver`. However, it's also possible to
43// adapt it to custom function names (say `AddFoo` and `RemoveFoo` accordingly)
Andrew Rayskiy3cf073392022-11-11 00:31:49[diff] [blame]44// by tailoring ScopedObservationTraits<> for the given Source and Observer --
45// see `base/scoped_observation_traits.h` for details.
Andrew Rayskiy799ce712022-11-04 22:42:53[diff] [blame]46//
47
Andrew Rayskiy3cf073392022-11-11 00:31:49[diff] [blame]48template <class Source, class Observer>
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]49class ScopedMultiSourceObservation {
50 public:
51 explicit ScopedMultiSourceObservation(Observer* observer)
52 : observer_(observer) {}
53 ScopedMultiSourceObservation(const ScopedMultiSourceObservation&) = delete;
54 ScopedMultiSourceObservation& operator=(const ScopedMultiSourceObservation&) =
55 delete;
56 ~ScopedMultiSourceObservation() { RemoveAllObservations(); }
57
58 // Adds the object passed to the constructor as an observer on |source|.
59 void AddObservation(Source* source) {
Peter Kasting013e36452024-02-03 13:15:28[diff] [blame]60 CHECK(!IsObservingSource(source));
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]61 sources_.push_back(source);
Andrew Rayskiy799ce712022-11-04 22:42:53[diff] [blame]62 Traits::AddObserver(source, observer_);
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]63 }
64
65 // Remove the object passed to the constructor as an observer from |source|.
66 void RemoveObservation(Source* source) {
Peter Kasting025a94252025-01-29 21:28:37[diff] [blame]67 auto it = std::ranges::find(sources_, source);
Peter Boström1aec0b22023-02-24 00:33:06[diff] [blame]68 CHECK(it != sources_.end());
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]69 sources_.erase(it);
Andrew Rayskiy799ce712022-11-04 22:42:53[diff] [blame]70 Traits::RemoveObserver(source, observer_);
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]71 }
72
Sigurdur Asgeirsson11031652020-11-12 17:44:25[diff] [blame]73 // Remove the object passed to the constructor as an observer from all sources
74 // it's observing.
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]75 void RemoveAllObservations() {
Andrew Rayskiy799ce712022-11-04 22:42:53[diff] [blame]76 for (Source* source : sources_) {
77 Traits::RemoveObserver(source, observer_);
78 }
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]79 sources_.clear();
80 }
81
Sigurdur Asgeirsson11031652020-11-12 17:44:25[diff] [blame]82 // Returns true if any source is being observed.
83 bool IsObservingAnySource() const { return !sources_.empty(); }
84
85 // Returns true if |source| is being observed.
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]86 bool IsObservingSource(Source* source) const {
Sigurdur Asgeirsson61cc21542020-11-19 00:12:07[diff] [blame]87 DCHECK(source);
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]88 return base::Contains(sources_, source);
89 }
90
Sigurdur Asgeirsson11031652020-11-12 17:44:25[diff] [blame]91 // Returns the number of sources being observed.
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]92 size_t GetSourcesCount() const { return sources_.size(); }
93
Theo Cristea09b94562024-09-04 08:07:31[diff] [blame]94 // Returns a pointer to the observer that observes the sources.
95 Observer* observer() { return observer_; }
96 const Observer* observer() const { return observer_; }
97
minch67592412024-01-05 17:20:59[diff] [blame]98 // Returns the sources being observed. Note: It is invalid to add or remove
99 // sources while iterating on it.
Julie Jeongeun Kim61027f82024-01-16 08:18:03[diff] [blame]100 const std::vector<raw_ptr<Source>>& sources() const { return sources_; }
minch67592412024-01-05 17:20:59[diff] [blame]101
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]102 private:
Andrew Rayskiy3cf073392022-11-11 00:31:49[diff] [blame]103 using Traits = ScopedObservationTraits<Source, Observer>;
Andrew Rayskiy799ce712022-11-04 22:42:53[diff] [blame]104
Keishi Hattori0e45c022021-11-27 09:25:52[diff] [blame]105 const raw_ptr<Observer> observer_;
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]106
Julie Jeongeun Kim61027f82024-01-16 08:18:03[diff] [blame]107 std::vector<raw_ptr<Source>> sources_;
Sigurdur Asgeirsson1a164fd2020-11-05 20:13:17[diff] [blame]108};
109
110} // namespace base
111
112#endif // BASE_SCOPED_MULTI_SOURCE_OBSERVATION_H_