【C++设计模式】行为型模式：观察者模式

行为型模式：观察者模式

观察者模式定义了一种一对多的依赖关系：它让一个主题（被观察者）对象关联多个观察者对象，并且当主题对象的状态发生变化时，它会主动通知这些观察者对象，使它们能够自动更新自己或执行相应的响应操作。

以一个设备的温度显示系统为例，在这个示例中，温度检测仪是被观察者，当设备温度发生变化时，它会通知所有的显示器更新温度信息。

#include <iostream>
#include <vector>
#include <string>
#include <algorithm> // 观察者接口
class IObserver {
public:virtual void update(float temperature) = 0;virtual ~IObserver() {}
};// 主题接口（Subject）
class ISubject {
public:virtual void registerObserver(IObserver* observer) = 0;virtual void removeObserver(IObserver* observer) = 0;virtual void notifyObservers() = 0;virtual ~ISubject() {}
};// 被观察者类：设备温度检测仪
class DeviceTemperatureMonitor : public ISubject {
private:std::vector<IObserver*> observers;float temperature;public:// 注册观察者void registerObserver(IObserver* observer) override {observers.push_back(observer);}// 移除观察者void removeObserver(IObserver* observer) override {// std::remove将所有与指定值observer相等的元素移动到容器的末尾，并返回指向第一个不需要保留的元素的迭代器observers.erase(std::remove(observers.begin(), observers.end(), observer), observers.end());}// 通知所有观察者void notifyObservers() override {for (IObserver* observer : observers) {observer->update(temperature);}}// 设置温度状态并通知所有观察者void setTemperature(float temp) {temperature = temp;notifyObservers();}
};// 观察者类：手机显示器
class PhoneDisplay : public IObserver {
private:std::string deviceName;public:PhoneDisplay(const std::string& name) : deviceName(name) {}void update(float temperature) override {std::cout << "Phone Display (" << deviceName << ") - Device Temperature: " << temperature << "°C\n";}
};// 观察者类：窗口显示器
class WindowDisplay : public IObserver {
private:std::string location;public:WindowDisplay(const std::string& loc) : location(loc) {}void update(float temperature) override {std::cout << "Window Display at " << location << " - Device Temperature: " << temperature << "°C\n";}
};int main() {// 创建被观察者对象（设备温度检测仪）DeviceTemperatureMonitor tempMonitor;// 创建观察者对象（显示设备）PhoneDisplay phoneDisplay1("iPhone");PhoneDisplay phoneDisplay2("Samsung");WindowDisplay windowDisplay("Office");// 注册观察者tempMonitor.registerObserver(&phoneDisplay1);tempMonitor.registerObserver(&phoneDisplay2);tempMonitor.registerObserver(&windowDisplay);// 模拟温度数据更新std::cout << "Temperature Update 1:\n";tempMonitor.setTemperature(75.0f);std::cout << "\nTemperature Update 2:\n";tempMonitor.setTemperature(80.0f);// 移除一个观察者tempMonitor.removeObserver(&phoneDisplay2);std::cout << "\nTemperature Update 3 (After removing Samsung Phone Display):\n";tempMonitor.setTemperature(85.0f);return 0;
}

Temperature Update 1:
Phone Display (iPhone) - Device Temperature: 75°C
Phone Display (Samsung) - Device Temperature: 75°C
Window Display at Office - Device Temperature: 75°CTemperature Update 2:
Phone Display (iPhone) - Device Temperature: 80°C
Phone Display (Samsung) - Device Temperature: 80°C
Window Display at Office - Device Temperature: 80°CTemperature Update 3 (After removing Samsung Phone Display):
Phone Display (iPhone) - Device Temperature: 85°C
Window Display at Office - Device Temperature: 85°C