可调用对象包装器

std::function是可调用对象的包装器。它是一个类模板，可以容纳除了类成员(函数)指针之外的所有可调用对象。通过指定它的模板参数，它可以用统一的方式处理函数，函数对象，函数指针，并允许保存和延迟执行它们。

基本用法:

std::function必须要包含一个叫做functional的头文件，可调用对象包装器使用语法如下:

#include <functional>
std::function<返回值类型(参数类型列表)> diy_name = 可调用对象;

1.包装普通函数

2.包装类的静态函数

3.包装仿函数

4.包装转换成函数指针的对象

代码如下:

#include <iostream>
#include <functional>
#include <string>
using namespace std;void print(int num, string name)
{cout << "id = "<<name << ",age = " << num << endl;
}using funcptr = void(*)(int, string);class Test
{
public:static void world(int a, string s){cout << "number = " << a << ",name = " << s << endl;}void operator()(string msg){cout << "仿函数:" << msg << endl;}operator funcptr(){return world;}
};int main()
{//1.包装普通函数function<void(int, string)> f1 = print;//2.包装类的静态方法function<void(int, string)> f2 = Test::world;//3.包装仿函数Test ta;function<void(string)> f3 = ta;//4.包装转换成函数指针的对象Test tb;function<void(int, string)> f4 = tb;//调用f1(1, "ace");f2(2, "tom");f3("jack");f4(3, "lily");return 0;
}

测试结果:

代码如下:

#include <iostream>
#include <functional>
#include <string>
using namespace std;class A
{
public:A(const function<void(int, string)> &f) :callback(f){}void notify(int id, string name){callback(id, name);}private:function<void(int, string)> callback;
};void print(int num, string name)
{cout << "id = " << name << ",age = " << num << endl;
}using funcptr = void(*)(int, string);class Test
{
public:static void world(int a, string s){cout << "number = " << a << ",name = " << s << endl;}void operator()(string msg){cout << "仿函数:" << msg << endl;}operator funcptr(){return world;}
};int main()
{//1.包装普通函数function<void(int, string)> f1 = print;//2.包装类的静态方法function<void(int, string)> f2 = Test::world;//3.包装仿函数Test ta;function<void(string)> f3 = ta;//4.包装转换成函数指针的对象Test tb;function<void(int, string)> f4 = tb;A aa(print);aa.notify(1, "tom");A ab(Test::world);ab.notify(2, "jack");A ac(tb);ac.notify(3, "luf");return 0;
}

测试结果: