可調(diào)用對(duì)象包裝器

std::function是可調(diào)用對(duì)象的包裝器。它是一個(gè)類模板，可以容納除了類成員(函數(shù))指針之外的所有可調(diào)用對(duì)象。通過(guò)指定它的模板參數(shù)，它可以用統(tǒng)一的方式處理函數(shù)，函數(shù)對(duì)象，函數(shù)指針，并允許保存和延遲執(zhí)行它們。

基本用法:

std::function必須要包含一個(gè)叫做functional的頭文件，可調(diào)用對(duì)象包裝器使用語(yǔ)法如下:

#include <functional> std::function<返回值類型(參數(shù)類型列表)> diy_name = 可調(diào)用對(duì)象;

1.包裝普通函數(shù)

2.包裝類的靜態(tài)函數(shù)

3.包裝仿函數(shù)

4.包裝轉(zhuǎn)換成函數(shù)指針的對(duì)象

代碼如下:

#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 << "仿函數(shù):" << msg << endl;}operator funcptr(){return world;} };int main() {//1.包裝普通函數(shù)function<void(int, string)> f1 = print;//2.包裝類的靜態(tài)方法function<void(int, string)> f2 = Test::world;//3.包裝仿函數(shù)Test ta;function<void(string)> f3 = ta;//4.包裝轉(zhuǎn)換成函數(shù)指針的對(duì)象Test tb;function<void(int, string)> f4 = tb;//調(diào)用f1(1, "ace");f2(2, "tom");f3("jack");f4(3, "lily");return 0; }

測(cè)試結(jié)果:

代碼如下:

#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 << "仿函數(shù):" << msg << endl;}operator funcptr(){return world;} };int main() {//1.包裝普通函數(shù)function<void(int, string)> f1 = print;//2.包裝類的靜態(tài)方法function<void(int, string)> f2 = Test::world;//3.包裝仿函數(shù)Test ta;function<void(string)> f3 = ta;//4.包裝轉(zhuǎn)換成函數(shù)指針的對(duì)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; }

測(cè)試結(jié)果:

總結(jié)

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