Error in calling a pointer to member function

Question

I have created a class with a member function and a structure which has a function pointer to the member function as an attribute. I have initialized the structure with the address of the member function. Then I have created an object for that class in main function and invoked the pointer to a member function by "(->*)". But It was failed with an error stating that "error: 'right operand' was not declared in this scope"

//Header
#ifndef A_H
#define A_H

class A
{
    public:
    typedef struct
    {
        void (A::*fptr) ();
    }test;

    test t;

    public:
        A();
        virtual ~A();
        void display();
    protected:

    private:
};
#endif // A_H


//A.cpp
#include "A.h"
#include <iostream>

using namespace std;

A::A()
{
    t.fptr = &A::display;
}

A::~A()
{
    //dtor
}

void A::display()
{
    cout << "A::Display function invoked" << endl;
}

//Main

#include <iostream>
#include "A.h"

using namespace std;

int main()
{
    cout << "Pointer to Member Function!" << endl;

    A *obj = new A;

    (obj->*t.fptr)();

    return 0;
}

||=== Build: Debug in fptr (compiler: GNU GCC Compiler) ===| In function 'int main()':| error: 't' was not declared in this scope| ||=== Build failed: 1 error(s), 0 warning(s) (0 minute(s), 1 second(s)) ===|

Answer 1

Pointer to member functions are always hard to get right. But you're almost there. First, change the invocation to

(obj->*obj->t.fptr)();

and then think again whether you really need to go with plain pointer to members nested in a struct of the very same class you're pointing into, or whether some type aliases or other approaches could beautify the above monster :)