函数从唯一代码调用正确的子类方法

Question

我想使用一个泛型函数来调用子类的适当方法

这是我在C ++中发现的一个问题，通常可以使用其他OOP语言（CLOS，python）解决，但我对C ++的了解不足以解决此问题。

这是一个注释的代码：我不知道如何在C ++中解决这个问题谢谢

#include <memory>
#include <cstdlib>

struct s_A
{
    //  virtual ~A() {}
    int numFunct()
    {
        printf("\n... running s_A method");
        // basic behaviour
        return 10;
    }
};

struct s_B : s_A
{
    int numFunct()
    {
        printf("\n... running s_B method");
        // customized behaviour for s_B instances here
        return 20;
    } 
};

struct s_C : s_A
{
    int numFunct()
    {
        printf("\n... running s_C method");
        // customized behaviour for s_C instances here
        return 30;
    } 
};

// want to code a unique giveIntanceNum function but with personalized behavior
// depending on the type of the argument
// I guess the problem is in argument declaration ?
int giveIntanceNum(s_A * myInstance)
{
    // ...
    // code here is long enough not to be recoded for every customized subclass
    // ....
    return myInstance->numFunct();
}


int main() //testing
{
    s_B * B = new s_B;
    s_C * C = new s_C;
    printf("\nReturned values calling method directly are %d and %d   ", B->numFunct(), C->numFunct());
    printf("\nReturned values calling through function are %d and %d   ", giveIntanceNum(B), giveIntanceNum(C));
    // I would like to get 20 for B and 30 for C as numFunct is called for a B (C) instance not an A
}

/* OUTPUT
... running s_C method
... running s_B method
Returned values calling method directly are 20 and 30   
... running s_A method
... running s_A method
Returned values calling through function are 10 and 10  
*/

Answer 1

虚拟的把戏。我离得很近，但是现在可以了

感谢伊戈尔

回答我的问题以备将来参考

struct s_A
{
    //  virtual ~A() {}
    virtual int numFunct()
    {
        printf("\n... running s_A method");
        return 10;
    }
};
...

/* OUTPUT
... running s_C method
... running s_B method
Returned values calling method directly are 20 and 30   
... running s_C method
... running s_B method
Returned values calling through function are 20 and 30 
*/