Question

#include "stdafx.h"
#include <iostream>
using namespace std;

class thing{
public:
    int stuff, stuff1, stuff2;

    void thingy(int stuff, int *stuff1){
        stuff2=stuff-*stuff1;
    }
}

int main(){
    thing t;
    int *ptr=t.stuff1;
    t.thingy(t.stuff, *ptr);
}

I’ve been practicing classes, and pointers in C++. What i’m trying to do is have the function thingy modify the stuff2 data member in the thing class by passing a pointer to the value of stuff1. How do I go about doing this?

Answer 1

You are creating a variable of type pointer-to-int: if you want a pointer to t.stuff1, take its address:

int* ptr = &t.stuff1;
        ___^ here you are taking a reference (address)

Then, pass that pointer to your thing::thingy method:

t.thingy(t.stuff, ptr);
                __^ don't dereference the pointer, your function takes a pointer