C++观察者与事件系统

张

张建站

2026/6/20 4:14:20

10分钟阅读

C观察者与事件系统观察者模式定义一对多依赖当一个对象状态变化时所有依赖对象自动收到通知。这是事件驱动系统的核心模式。基本观察者模式包含主题和观察者接口。#include#include#include#include#include#includeclass Observer {public:virtual ~Observer() default;virtual void on_notify(const std::string event, const std::string data) 0;virtual int id() const 0;};class Subject {std::vector observers_;public:void attach(std::shared_ptr obs) {observers_.push_back(obs);std::cout Observer obs-id() attached\n;}void detach(std::shared_ptr obs) {auto it std::find_if(observers_.begin(), observers_.end(),[obs](const auto o) { return o-id() obs-id(); });if (it ! observers_.end()) {observers_.erase(it);}}void notify(const std::string event, const std::string data) {for (auto obs : observers_) {obs-on_notify(event, data);}}};class ConcreteObserver : public Observer {int id_;std::string name_;public:ConcreteObserver(int id, const std::string name) : id_(id), name_(name) {}void on_notify(const std::string event, const std::string data) override {std::cout Observer name_ (ID: id_ ): Event event , Data data \n;}int id() const override { return id_; }};void observer_demo() {Subject subject;auto obs1 std::make_shared(1, Logger);auto obs2 std::make_shared(2, Display);subject.attach(obs1);subject.attach(obs2);subject.notify(data_changed, Hello World);subject.detach(obs2);subject.notify(update, After detach);}带事件过滤的观察者系统。enum class EventType {ALL 0,DATA_CHANGE,ERROR,STATUS};class FilteredObserver : public Observer {int id_;std::string name_;std::vector subscribed_events_;public:FilteredObserver(int id, const std::string name, std::vector events): id_(id), name_(name), subscribed_events_(events) {}void on_notify(const std::string event, const std::string data) override {std::cout Filtered name_ : event - data \n;}int id() const override { return id_; }bool is_interested(EventType type) const {if (subscribed_events_.empty()) return true;return std::find(subscribed_events_.begin(), subscribed_events_.end(), type)! subscribed_events_.end();}};基于回调的事件系统。class EventEmitter {std::vector listeners_;public:void add_listener(std::function listener) {listeners_.push_back(std::move(listener));}void emit(const std::string event, int value) {for (auto listener : listeners_) {listener(event, value);}}};void callback_event_demo() {EventEmitter emitter;emitter.add_listener([](const std::string evt, int val) {std::cout Listener 1: evt val \n;});int total 0;emitter.add_listener([total](const std::string evt, int val) {total val;std::cout Listener 2: total total \n;});emitter.emit(click, 10);emitter.emit(scroll, 20);}可断开的连接。class Connection {std::function disconnect_fn_;public:Connection() default;explicit Connection(std::function fn) : disconnect_fn_(std::move(fn)) {}void disconnect() {if (disconnect_fn_) {disconnect_fn_();disconnect_fn_ nullptr;}}Connection(Connection other) noexcept: disconnect_fn_(std::move(other.disconnect_fn_)) {}};class DisconnectableEmitter {std::map slots_;int next_id_ 0;public:Connection connect(std::function slot) {int id next_id_;slots_[id] std::move(slot);return Connection([this, id]() { slots_.erase(id); });}void emit(int value) {for (auto [id, slot] : slots_) {slot(value);}}};void disconnectable_demo() {DisconnectableEmitter emitter;auto conn1 emitter.connect([](int v) {std::cout Slot 1: v \n;});auto conn2 emitter.connect([](int v) {std::cout Slot 2: v * 2 \n;});emitter.emit(10);conn1.disconnect();emitter.emit(20);}观察者模式是MVC架构和事件驱动系统的基础。