根据变量调用函数？

Question

你能根据整数是一个函数来调用函数吗？

这就是我的意思:

#include <iostream>

using namespace std;

int whichFunction;

int main()
{
    cout << "Which function do you want to call?";
    cin >> whichFunction;

    function[whichFunction](); 
    //If you entered 1, it would call function1 - same with 2, 3
    //or Hihihi (of course only when whichFunction would be a string)
}


void function1()
{
    cout << "Function No. 1 was called!";
}

void function2()
{
    cout << "Function No. 2 was called!";
}

void functionHihihi()
{
    cout << "Function Hihihi was called!";
}

我知道这不起作用,但我希望你明白这个想法.

有没有办法做这样的事情？

Answer 1

是的,有办法做到这一点.

//Array for the functions
std::array<std::function<void()>, 3> functions = { &function1, &function2, &function3 };

//You could also just set them manually
functions[0] = &function1;
functions[1] = &function2;
functions[2] = &function3;

然后你可以将它用作普通数组:

functions[whichFunction](); //Calls function number 'whichFunction'

请注意,所有功能都必须具有相同的签名.

如果std::function由于某种原因不想使用,可以使用函数指针.

Answer 2

switch(whichFunction) {
    case 1: function1(); break;
    case 2: function2(); break;
    case 3: function3(); break;
}

Answer 3

使用指针函数是一件好事:

#include <iostream>
#include <string>
using namespace std;


void foo1(){cout << "Foo1 says hello!" << endl;}
void foo2(){cout << "Foo2 says hello!" << endl;}
void foo3(){cout << "Foo3 says hello!" << endl;}
void foo4(){cout << "Foo4 says hello!" << endl;}


int main()
{

    system("color 1f");

    int input;
    cout << "Which function you wanna call: ";
    cin >> input;
    cout << endl;


    void (*pFunc)() = NULL;

    switch(input)
    {
        case 1:
            pFunc = foo1;
        break;
        case 2:
            pFunc = foo2;
        break;
        case 3:
            pFunc = foo3;
        break;
        default:
            cout << "No function available!" << endl;
    }

    if(NULL != pFunc) //avoiding usage of a NULL ptr
        (*pFunc)();

    cout << endl << endl << endl;
    return 0;
}