在C++中存在"可調用對象"這么一個概念，準確來說，可調用對象有如下幾種定義:

1.是一個函數指針

代碼如下:

int print(int a, double b) {cout << a << b << endl;return 0; }int(*func)(int, double) = &print;

2.是一個具有operator()成員函數的類對象(仿函數)

代碼如下:

#include <vector> #include <iostream> #include <string>using namespace std;using func_ptr = void(*)(int, string);struct Test {void operator()(int x){cout << "x = " << x << endl;} };int main() {Test t1;t1(19);return 0; }

測試結果:

3.是一個可被轉換為函數指針的類對象

代碼如下:

#include <vector> #include <iostream> #include <string>using namespace std;using func_ptr = void(*)(int, string);struct Test {static void print(int a, string b){cout << "name = " << b << ",age = " << a << endl;}//將類對象轉換成函數指針operator func_ptr(){return print;//需要是靜態函數} };int main() {Test t1;t1(19, "nihao");return 0; }

測試結果:

4.是一個類成員函數指針或者類成員指針

代碼如下:

#include <vector> #include <iostream> #include <string>using namespace std;using funcptr = void(*)(int, string);struct Test {static void print(int a, string b){cout << "name = " << b << ",age = " << a << endl;}void hello(int a, string b){cout << "name = " << b << ",age = " << a << endl;}int id = 520;};int main() {Test t1;funcptr f = Test::print;//類的函數指針using fptr = void(Test::*)(int, string);fptr f1 = &Test::hello;//類的成員指針(變量)using ptr1 = int Test::*;ptr1 pt = &Test::id;Test ttt;(ttt.*f1)(20, "tom");ttt.*pt = 100;cout << "id = " << ttt.id << endl;return 0; }

測試結果:

總結

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