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回调函数的概念

news 2025/10/24 14:01:35

回调函数的基本概念

回调函数的本质是"你定义，我调用" - 你提供一个函数，系统或框架在特定时机调用它。

实现回调函数的几种方式

1. 函数指针（传统方式）

#include <iostream>// 回调函数类型定义
typedef void (*Callback)(int, const std::string&);// 接受回调函数的函数
void processData(int value, const std::string& name, Callback callback) {std::cout << "处理数据中..." << std::endl;// 处理完成后调用回调函数callback(value, name);
}// 具体的回调函数实现
void myCallback(int num, const std::string& text) {std::cout << "回调函数被调用: " << num << ", " << text << std::endl;
}int main() {processData(42, "Hello", myCallback);return 0;
}

2. std::function（现代方式）

#include <iostream>
#include <functional>void processData(int value, const std::string& name, std::function<void(int, const std::string&)> callback) {std::cout << "处理数据中..." << std::endl;callback(value, name);
}void myCallback(int num, const std::string& text) {std::cout << "回调函数被调用: " << num << ", " << text << std::endl;
}int main() {// 使用函数指针processData(42, "World", myCallback);// 使用lambda表达式processData(100, "Lambda", [](int n, const std::string& s) {std::cout << "Lambda回调: " << n << ", " << s << std::endl;});return 0;
}

3. 函数对象（Functor）

#include <iostream>class MyCallback {
public:void operator()(int value, const std::string& message) {std::cout << "函数对象回调: " << value << ", " << message << std::endl;}
};template<typename CallbackType>
void processData(int value, const std::string& name, CallbackType callback) {std::cout << "处理数据中..." << std::endl;callback(value, name);
}int main() {MyCallback callbackObj;processData(200, "Functor", callbackObj);return 0;
}

实际应用示例

事件处理系统

#include <iostream>
#include <functional>
#include <vector>class Button {
private:std::vector<std::function<void()>> clickCallbacks;public:// 注册点击回调void onClick(std::function<void()> callback) {clickCallbacks.push_back(callback);}// 模拟按钮点击void click() {std::cout << "按钮被点击!" << std::endl;for (auto& callback : clickCallbacks) {callback();}}
};int main() {Button btn;// 注册多个回调函数btn.onClick([]() {std::cout << "执行操作1: 保存文件" << std::endl;});btn.onClick([]() {std::cout << "执行操作2: 更新界面" << std::endl;});// 模拟点击btn.click();return 0;
}

异步操作回调

#include <iostream>
#include <functional>
#include <thread>
#include <chrono>void asyncOperation(std::function<void(bool, const std::string&)> callback) {std::thread([callback]() {std::cout << "开始异步操作..." << std::endl;std::this_thread::sleep_for(std::chrono::seconds(2));// 模拟操作完成bool success = true; // 或 falsestd::string result = "操作完成";callback(success, result);}).detach();
}int main() {std::cout << "主线程继续执行..." << std::endl;asyncOperation([](bool success, const std::string& message) {if (success) {std::cout << "成功: " << message << std::endl;} else {std::cout << "失败: " << message << std::endl;}});// 等待异步操作完成std::this_thread::sleep_for(std::chrono::seconds(3));return 0;
}