Question

我有以下代码

#include<iostream>
using namespace std;
class operate
{
    int x;
    int y;
public:
    operate(int _x, int _y):x(_x), y(_y)
    {}
    void add(const char* ch)
    {
        cout<<ch<<" "<<x+y;
    }
    void subtract(const char* ch)
    {
        cout<<ch<<" "<<x-y;
    }
    void multiply(const char* ch)
    {
        cout<<ch<<" "<<x*y;
    }
};
int main()
{
    void (operate::*fptr[3])(const char*);
    operate obj(2,3);
    fptr[0] = &(operate.add);              //problem
    fptr[1] = &(operate.multiply);         //problem
    fptr[2] = &(operate.subtract);         //problem
    (obj.*fptr[0])("adding");
    (obj.*fptr[1])("multiplying");
    (obj.*fptr[2])("subtracting");
}

似乎我没有正确地将成员函数分配给函数指针数组。我该怎么解决这个问题。我正在使用VS2010

Answer 1

dot（member-of）运算符用于访问对象的成员。对于类和名称空间，您必须使用::运算符。另外，请勿使用括号，因为&的优先级低于::，而且它的可读性更高

fptr[0] = &operate::add;

Answer 2

这应该做的工作

void testFP()
{
    typedef void (operate::*memFP)(const char*); 
    memFP fptr[3];

    fptr[0] = &operate::add;
    fptr[1] = &operate::multiply;
    fptr[2] = &operate::subtract;
    operate op(42, 42);

    (op.*(fptr[0]))("adding");
}

成员函数的函数指针数组

2 个答案: