8.4类成员函数的指针与多态性

1 类成员函数的指针

2 类成员函数的指针数组

3 指向类成员函数的指针的指针

1 类成员函数的指针

auto func1 = &com::jia;//C++函数指针

int (com::*p)(int, int) = &com::jia;//C函数指针

#include <iostream>

class com
{
private:
    int a;
    int b;
public:
    com(int x, int y) :a(x), b(y)
    {

    }
    int jia(int a, int b)
    {
        return a + b;
    }
    int jian(int a, int b)
    {
        return a - b;
    }
    int cheng(int a, int b)
    {
        return a*b;
    }
    double chu(int a, int b)
    {
        return a / b;
    }
};

void main()
{
    com com1(100, 20);

    auto func1 = &com::jia;//C++函数指针
    int (com::*p)(int, int) = &com::jia;//C函数指针
    
    std::cout << typeid(func1).name() << std::endl;//打印数据类型，上下一样
    std::cout << typeid(p).name() << std::endl;//打印数据类型，上下一样

    system("pause");
}

2 类成员函数的指针数组

typedef int(com::*P)(int, int);

P func1[4] = { &com::jia ,&com::jian,&com::cheng,&com::chu };//使用typedef

int(com::*func2[4])(int, int) = { &com::jia ,&com::jian,&com::cheng,&com::chu };//不使用typedef

#include <iostream>

class com
{
private:
    int a;
    int b;
public:
    com(int x, int y) :a(x), b(y)
    {

    }
    int jia(int a, int b)
    {
        return a + b;
    }
    int jian(int a, int b)
    {
        return a - b;
    }
    int cheng(int a, int b)
    {
        return a*b;
    }
    int chu(int a, int b)
    {
        return a / b;
    }
};

typedef int(com::*P)(int, int);

void main()
{
    com com1(100, 20);

    P func1[4] = { &com::jia ,&com::jian,&com::cheng,&com::chu };//使用typedef

    int(com::*func2[4])(int, int) = { &com::jia ,&com::jian,&com::cheng,&com::chu };//不使用typedef
    
    for (int i = 0; i < 4; i++)
    {
        std::cout << (com1.*func1[i])(10, 20) << std::endl;
        std::cout << (com1.*func2[i])(10, 20) << std::endl;
        std::cout << std::endl;
    }
    
    system("pause");
}

3 指向类成员函数的指针的指针

#include <iostream>

class com
{
private:
    int a;
    int b;
public:
    com(int x, int y) :a(x), b(y)
    {

    }
    int jia(int a, int b)
    {
        return a + b;
    }
    int jian(int a, int b)
    {
        return a - b;
    }
    int cheng(int a, int b)
    {
        return a*b;
    }
    int chu(int a, int b)
    {
        return a / b;
    }
};

typedef int(com::*P)(int, int);

void main()
{
    com com1(100, 20);

    P func1[4] = { &com::jia ,&com::jian,&com::cheng,&com::chu };//使用typedef

    int(com::*func2[4])(int, int) = { &com::jia ,&com::jian,&com::cheng,&com::chu };//不使用typedef

    int(com::**funcp)(int, int) = func1;//二级指针，指向类成员函数的指针的指针

    for (; funcp < func1 + 4; funcp++)//指针遍历数组
    {
        std::cout << (com1.**funcp)(10, 20) << std::endl;
    }
    
    system("pause");
}