Question

The problem is that class A depends on class B and vice versa. The compiler will complain abount an unknown type. The usual solution is to forward-declare the classes. But how to declare template classes?

Answer 1

I took me a while to find a solution so I thought i could make somebody else’s life easier by posting a “template” here.

// Header A.h
template<class z, class w = float>
class B;

template<class x, class y = double>
class A
{
    B mb;
}


// Header B.h
template<class x, class y = double>
class A;

template<class z, class w = float>
class B
{
    A mA;
}

Furthermore you are able to change the optional parameter in the template declaration.