C++ - dereferencing pointers that are elements of an array?

Question

I have an object of a Deck class which contains a dynamically allocated array of pointers to objects of another class, PlayingCard. I'm attempting to overload the << operator (as a friend of class Deck) to output details of each card in a Deck object iteratively. At present the overload definition looks like this:

ostream& operator<< (ostream& out, const Deck& d)
{
    PlayingCard** pCards = d.getPlayingCards();
    for(int i = 0; i < d.getTotalCards(); ++i)
    {
        out << pCards[i] << endl;
        // the << operator is also overloaded in the PlayingCard class to take PlayingCard objects as arguments.
        // the overload in the PlayingCard class definitely works.
    }

    return out;
}

When attempting to construct a Deck object and output its card details, it outputs a list of memory addresses rather than actual data, so I guess I need to dereference pCards[i]. When I try to do that, however, the output is garbage and I eventually reach an access violation in the debugger. I've tried all of the following combos, but all cause either compile-time or run-time problems:

*pCards[i], pCards[i]*, (*pCards[i]), *(pCards[i])

Is this just incorrect syntax for dereferencing a pointer that's within an array, or is there something deeper I'm not understanding here? How can I rewrite this code so the program outputs the actual data held by these PlayingCard objects, rather than just the memory addresses?

Answer 1

*pCards[i] , (*pCards[i]) and *(pCards[i]) are all dereferencing the objects. There is something else going wrong in another part of your program, probably in the implementation of Deck .

Answer 2

ostream& operator<< (ostream& out, const Deck& d)
{
    PlayingCard** pCards = d.getPlayingCards();
    for(int i = 0; i < d.getTotalCards(); ++i)
        out << (*(pCards[i])) << endl;  
    return out;
}

You are passing pCards[i] which is a pointer to PlayingCard ( = PlayingCard * ). There won't be operator<< method overloaded for that so you need *(pCards[i]) but then you must also ensure that you have the commensurate overloading for class PlayingCard . ie a friend function with signature:

ostream& operator<< (ostream& out, const PlayingCard& d);

Oops, just read your comments:

        // the << operator is also overloaded in the PlayingCard class to take PlayingCard objects as arguments.
        // the overload in the PlayingCard class definitely works.

Are you sure that method is visible to the function you have shown code for above?