Thread: Forward declaration of classes

this was not a requirement of my software design parameters. I was just wondering if there was a way it could be done.

This class hierarchy has a class called Object as its base, and a class called String derives publicly from Object. I wanted Object to have a virtual ToString() function that would return a String type. it's beginning to look like this is not possible. it's not really a setback though. since I was planning a ToString() member function in each derived class anyway, It doesn't really matter that it's not a virtual function.

All of your advice and suggestions have been wonderful, and I appreciate all of you taking your time to help with my question.

Originally Posted by CornedBee

You don't need the definition of a class to declare a function with that class as the return type. This little example compiles without problems:

Code:

class B;

class A
{
public:
        B getB();
};

class B : public A
{
};

B A::getB() { return B(); }

int main()
{
        A a;
        B b(a.getB());
}

That one kind of surprised me for a second; but then I realized it's only if you want a B member variable in A that you need to make it a pointer...

>> it's beginning to look like this is not possible.
CornedBee showed an example that compiles and does exactly what you describe. Can you try compiling his example?

>> This little example compiles without problems
But that's not guaranteed in the standard, is it?

Originally Posted by Daved

>> This little example compiles without problems
But that's not guaranteed in the standard, is it?

Why not?

I'm not sure and I don't remember, but there was mention of a reason on here a few weeks (months?) ago. Something about how some compilers might require the size of that object to set up the stack properly or something.