How to use callback functions in C++?

Callback functions in C are implemented through function pointers or lambda expressions: Function pointer: define type void(*CallbackFunction)(int); register callback function: RegisterCallback(callback); call callback function: CallCallbacks(value); Example: The event handling class registers the callback function and triggers the event. Lambda expression: Register callback function: RegisterCallback(std::function callback); Call callback function: CallCallbacks(value); Example: Get user input and register callback function.

Usage of callback function in C

The callback function allows the function to return control to the caller, and then in some A function that is executed again when the condition is met. This is useful in event-driven programming, where one event may trigger multiple actions.

In C, callback functions can be implemented through function pointers or lambda expressions.

Use function pointers

// 定义一个函数指针类型
typedef void(*CallbackFunction)(int);

// 注册回调函数
void RegisterCallback(CallbackFunction callback) {
  // 将回调函数存储在列表中
  callbackList.push_back(callback);
}

// 调用回调函数
void CallCallbacks(int value) {
  for (auto callback : callbackList) {
    callback(value);
  }
}

// 实战案例：事件处理

// 定义一个事件处理类
class EventHandler {
public:
  void OnEvent() {
    // 调用注册的回调函数
    CallCallbacks(42);
  }
};

// 创建事件处理类实例
EventHandler eventHandler;

// 订阅事件的回调函数
RegisterCallback([](int value) {
  std::cout << "事件处理程序: " << value << std::endl;
});

// 触发事件
eventHandler.OnEvent();

Use lambda expression

Lambda expression was introduced in C 11, which provides a A concise way to define anonymous functions.

// 注册回调函数
void RegisterCallback(std::function<void(int)> callback) {
  // 将回调函数存储在列表中
  callbackList.push_back(callback);
}

// 调用回调函数
void CallCallbacks(int value) {
  for (auto callback : callbackList) {
    callback(value);
  }
}

// 实战案例：用户输入

// 创建一个获取用户输入的函数
std::string GetUserInput() {
  std::string input;
  std::cout << "输入一些文本：" << std::flush;
  std::cin >> input;
  return input;
}

// 订阅获取用户输入后的回调函数
RegisterCallback([](int value) {
  std::cout << "用户输入了：" << GetUserInput() << std::endl;
});

// 获取用户输入
GetUserInput();

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