c++ Forward Declaration design

Question

From what i've read, i should use forward declarations whenever I can. I have classes like this ( where every fields are pointers because of forward declarations ) :

class A
{
    // ...

    A* a;
    B* b;
    C* c;
    D* d;
    E* e;
};

But there is problems with that.

1- This implies to call new and delete ( or at least new with smart pointers ) for every fields in constructor, while stack allocated fields don't need this.

2- I've read that stack allocation was faster than heap allocation.

3- Also that means that almost every fields on every classes should be pointers.

Am I doing the right way doing like my example class? Or am I missing something with forward declarations?

Answer 1

The implication is inverse - you're not supposed to use pointers just in order to use forward declarations, but you're suppose to use forward declarations after you've taken a design decision (such as using pointers instead of objects as members) when you can.

So if it makes more sense to use objects, do so, and include the files you need. Don't use pointers just so you can forward-declare the classes.