Question

My C++ is little rusty. Can anyone see why I am seeing “not a class or namespace” compile-time error in main() while accessing i.

#include <iostream>

using namespace std;

class Singleton2 {
    Singleton2(){
        i = 0;
    }
public:
    int i;

    friend Singleton2 & singleton2();
};

Singleton2 & singleton2(){
    static Singleton2 ms;

    return ms;
}

int main() {
    Singleton2 ms = singleton2();
    int i = ms::i;              // error: `ms' is not a class or namespace
    cout << i << endl;
}

Answer 1

You use dot . operator to access non-static members, not the scope resolution operator ::

int i = ms.i;

Note that the assignment below

Singleton2 ms = singleton2();

makes a copy of your singleton. Your singleton2() returns a reference, so you should probably make ms a reference as well:

Singleton2 &ms = singleton2();