How to initialize a reference member variable inside a member function & access it inside other member functions - C++

Question

The usual method one'd use for normal variables (declaring outside the member functions & initializing inside a member function) doesn't work, as reference variables need to be initialized & declared in same line.

#include <iostream>
using namespace std;

class abc {
public:
    int& var; 
    void fun1 (int& temp) {var=temp;} 
    void fun2 () {cout << abc::var << endl;}
    abc() {}
};

int main() {
    abc f;
    int y=9;
    f.fun1(y);
    f.fun2();
    return 0;
}

Answer 1

How to initialize a reference member variable inside a member function & access it inside other member functions - C++

Use a pointer.

#include <iostream>
using namespace std;

class abc {
public:
    int* var; 
    void fun1 (int& temp) { var = &temp; } 
    void fun2 () { cout << *abc::var << endl; }
    abc() {}
};

int main() {
    abc f;
    int y=9;
    f.fun1(y);
    f.fun2();
    return 0;
}

Answer 2

I think this is the best you can do.

#include <iostream>
using namespace std;

class abc {
public:
    int& var; 
    abc(int& temp) :
       var(temp)
    {}
    void fun2 () {cout << abc::var << endl;}
};

int main() {
    int y=9;
    abc f(y);
    f.fun2();
    return 0;
}

A reference is a constant thing — it refers to the same integer for the entire lifespan of the object. That means you need to set it on construction.

Answer 3

int var; int& varref = abc::var;

This should work!