Forward declare typedef within C++ class

Question

What\'s the best solution to forward declare a typedef within a class. Here\'s an example of what I need to solve:

class A;
class B;

class A
{
    typedef boos         


        

Answer 1

You cannot.

But you can decouple the Ptr definition of the classes:

class A;
class B;

template 
struct Traits {
    typedef std::shared_ptr  Ptr; 
};

class A
{
    Traits::Ptr foo();
};

class B
{
    Traits::Ptr bar();
};

If A and B does not share the same types, you always can specialize Traits for all type.