C++ callback function - practical operation (2)

std::functionCallbacks are usually implemented through function pointers, function objects (functors), Lambda expressions, or .

1. Function pointer implements callback

This method of implementing callbacks is easier to remember. Just remember to pass the function as a parameter to the method and call the method in the method.

#include <iostream>

// 回调函数类型
typedef void (*CallbackFunction)(int);

// 使用回调函数的函数
void performCallback(int value, CallbackFunction callback) {
    // 执行某些操作
    std::cout << "Performing operation with value: " << value << std::endl;

    // 调用回调函数
    callback(value * 2);
}

// 回调函数
void callbackFunction(int value) {
    std::cout << "Callback executed with value: " << value << std::endl;
}

int main() {
    performCallback(5, callbackFunction);
    return 0;
}

2. Function object (functor) implements callback

#include <iostream>

// 仿函数类
class CallbackClass {
public:
    void operator()(int value) const {
        std::cout << "Callback executed with value: " << value << std::endl;
    }
};

// 使用回调函数对象的函数
void performCallback(int value, const CallbackClass& callback) {
    // 执行某些操作
    std::cout << "Performing operation with value: " << value << std::endl;

    // 调用回调函数对象
    callback(value * 2);
}

int main() {
    CallbackClass callbackObj;
    performCallback(5, callbackObj);
    return 0;
}

3. Lambda expression implements callback

#include <iostream>

// 使用回调Lambda的函数
void performCallback(int value, const std::function<void(int)>& callback) {
    // 执行某些操作
    std::cout << "Performing operation with value: " << value << std::endl;

    // 调用回调Lambda
    callback(value * 2);
}

int main() {
    // 定义并传递Lambda作为回调
    performCallback(5, [](int value) {
        std::cout << "Callback executed with value: " << value << std::endl;
    });
    return 0;
}

Recommended reading

C++ std::tr1::function and std::tr1::bind template class introduction, qt test-CSDN blog