我正在尝试以更好的方式掌握指针函数的概念。所以我有一个非常简单且有效的示例:

#include <iostream>

using namespace std;

int add(int first, int second)
{
    return first + second;
}

int subtract(int first, int second)
{
    return first - second;
}

int operation(int first, int second, int (*functocall)(int, int))
{
    return (*functocall)(first, second);
}

int main()
{
    int  a, b;
    int  (*plus)(int, int);
    int  (*minus)(int, int);
    plus = &add;
    minus = &subtract;
    a = operation(7, 5, add);
    b = operation(20, a, minus);
    cout << "a = " << a << " and b = " << b << endl;
    return 0;
}

到目前为止一切顺利 现在我需要将函数分组到一个类中，并根据我使用的函数指针选择加法或减法。所以我只是做了一个小修改:

#include <iostream>

using namespace std;

class A
{
public:
int add(int first, int second)
{
    return first + second;
}

int subtract(int first, int second)
{
    return first - second;
}

int operation(int first, int second, int (*functocall)(int, int))
{
    return (*functocall)(first, second);
}
};

int main()
{
    int  a, b;
    A a_plus, a_minus;
    int (*plus)(int, int) = A::add;
    int (*minus)(int, int) = A::subtract;
    a = a_plus.operation(7, 5, plus);
    b = a_minus.operation(20, a, minus);
    cout << "a = " << a << " and b = " << b << endl;
    return 0;
}

明显的错误是:

ptrFunc.cpp: In function ‘int main()’:
ptrFunc.cpp:87:29: error: invalid use of non-static member function ‘int A::add(int, int)’
ptrFunc.cpp:88:30: error: invalid use of non-static member function ‘int A::subtract(int, int)’

因为我还没有指定调用哪个对象(而且我现在不想使用静态方法)

编辑: 一些评论和答案表明非静态版本(如我所写)是不可能的。(感谢所有人) 所以， 以下列方式修改类也不起作用:

#include <iostream>

using namespace std;

class A
{
    int res;
public:
    A(int choice)
    {
        int (*plus)(int, int) = A::add;
        int (*minus)(int, int) = A::subtract;
        if(choice == 1)
            res = operation(7, 5, plus);
        if(choice == 2)
            res = operation(20, 2, minus);
        cout << "result of operation = " << res;
    }
int add(int first, int second)
{
    return first + second;
}

int subtract(int first, int second)
{
    return first - second;
}

int operation(int first, int second, int (*functocall)(int, int))
{
    return (*functocall)(first, second);
}
};

int main()
{
    int  a, b;
    A a_plus(1);
    A a_minus(2);
    return 0;
}

产生了这个错误:

ptrFunc.cpp: In constructor ‘A::A(int)’:
ptrFunc.cpp:11:30: error: cannot convert ‘A::add’ from type ‘int (A::)(int, int)’ to type ‘int (*)(int, int)’
ptrFunc.cpp:12:31: error: cannot convert ‘A::subtract’ from type ‘int (A::)(int, int)’ to type ‘int (*)(int, int)’

我可以知道如何解决这个问题吗？

谢谢

最佳答案

声明成员方法的函数指针的语法是:

int (A::*plus)(int, int) = &A::add;
int (A::*minus)(int, int) = &A::subtract;

要调用成员方法，请使用 .* 或 ->* 运算符:

 (a_plus.*plus)(7, 5);

另请查看 http://msdn.microsoft.com/en-us/library/b0x1aatf(v=vs.80).aspx

希望这对您有所帮助。

完整代码:

     #include <iostream>

    using namespace std;

    class A
    {
    public:
    int add(int first, int second)
    {
        return first + second;
    }

    int subtract(int first, int second)
    {
        return first - second;
    }

    int operation(int first, int second, int (A::*functocall)(int, int))
    {
        return (this->*functocall)(first, second);
    }
    };

    int main()
    {
        int  a, b;
        A a_plus, a_minus;
        int (A::*plus)(int, int) = &A::add;
        int (A::*minus)(int, int) = &A::subtract;
        a = a_plus.operation(7, 5, plus);
        b = a_minus.operation(20, a, minus);
        cout << "a = " << a << " and b = " << b << endl;
        return 0;
    }

关于c++ - 函数指针生成 'invalid use of non-static member function' 错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/15756331/