>> So my question really is: how can I tell the compiler that Class2 will be defined later.
If you preceed the two classes with forward references, as in:
class Class2;
class Class1;
then your code in
http:#33219489 compiles. If you start getting into compilation issues as you add items to your classes, then just remember that you can have two header files, one for each class, and two .cpp files - again, one for each class; and that may help you out of any difficulties.