Question

My class has a private enum whose members are being used to index an array of strings, the output of which is written to an output stream.

private:
    enum supportedMessageTypes(CRITICAL = 0, WARNING, INFORMATION);
    string messages[3];

//meanwhile, inside the constructor,
messages[3] = {"Critical error message", 
               "Warning message", 
               "Information message"};

Since I’m going to be using the enum values around my code a lot, I’d like to be able to overload operator<< to perform a lookup of the enum value, match it to the corresponding string in the array, and return that in the following manner:

cout << CRITICAL << ": " << messageText << std::endl;

The problem I have is that supportedMessageTypes is private while overloading of operator<< should be done as a non-member function. I know I can define a friend function that overloads operator<< for my class, but I’m simply not comfortable with breaking encapsulation in that way, and was wondering if anyone knew of a way to overload operator<< without using friend functions or making supportedMessageTypes public?

Answer 1

This isn’t possible. You want to accept an argument of type supportedMessageTypes, so it must be visible. There’s no way around it.

Also, a friend function wouldn’t be bad here; this is one of the intented scenarios for friendship.