C++ - 2 classes 1 file

Question

Suppose I want something of this sort, in one .cpp source file:

class A {
    public:
        void doSomething(B *b) {};
};

class B {
    publi         


        

Answer 1

forward declare one class before other with

class B;
or
class A;

But still you won't be able to implement

void doSomething(B *b)

using only forward declaration of B. So you have to put definition of doSomething below full class A declaration

Answer 2

Add another declaration of B before A:

class B;

class A {
    public:
        void doSomething(B *b) {};
};

class B {
    public:
        void doSomething(A *a) {};
};