C++ 回调函数示例

C++ 回调函数示例

简单示例

#include <functional>
#include <iostream>

void print() { std::cout << "print()" << std::endl; }

void callback(std::function<void()> func) {
  std::cout << "Enter: callback()" << std::endl;
  func();
  std::cout << "Leave: callback()" << std::endl;
}

int main() {
  callback(print);
  system("pause");
}

输出：

Enter: callback()

print()

Leave: callback()

接下来我们把这两个函数放入类中实现，在调用的时候绑定函数名和其对应实例就可以按以上例子方法调用。

#include <functional>
#include <iostream>

class operation {
public:
void print() { std::cout << "print()" << std::endl; }
};

class controller {
public:
void callback(std::function<void()> func) {
  std::cout << "Enter: callback()" << std::endl;
  func();
  std::cout << "Leave: callback()" << std::endl;
}
};

int main() {
  controller control;
  operation op;
  /// 绑定实例和对应的操作函数
  auto f = std::bind(&operation::print, &op);
  control.callback(f);
  system("pause");
}

现在我们把绑定函数对象的过程封装起来

#include <functional>
#include <iostream>

class operation {
 public:
  auto get_print_function() { return std::bind(&operation::print, this); }
  void print() { std::cout << "print()" << std::endl; }
};

class controller {
 public:
  void callback(std::function<void()> func) {
    std::cout << "Enter: callback()" << std::endl;
    func();
    std::cout << "Leave: callback()" << std::endl;
  }
};

int main() {
  controller control;
  operation op;
  control.callback(op.get_print_function());
  system("pause");
}