Re: Making virtual objects out of non-virtual objects
4zumanga@gmail.com wrote:
struct AnyVariable
{ tr1::shared_ptr<AnyPtr> p;
int foo() { return p->foo(); }
};
struct AnyPtr
{ virtual int foo() = 0; }
template<typename T>
struct AnyPtr_Concrete : public AnyPtr
{
T data;
virtual int foo() { return data.foo; }
};
With a little more nice wrapping, and neatening, I can now write:
AnyVariable(new AnyPtr_Concrete<A>(A)), and be able to pass around
objects that look like normal non-virtual classes, but act like
pointers to a virtual type heirachy.
The creation looks like it could use a bit of wrapping, i.e.
template<typename T> AnyVariable::AnyVariable(T t) {
tr1::shared_ptr<AnyPtr>(new AnyPtr_Concrete<T> ptr);
ptr->data = t;
this->p = ptr;
}
You can now write
AnyVariable x = A(5);
Personally, I think AnyPtr is a misleading name. It's not a pointer,
but
an abstract base class. Furthermore, if you're careful, you can use
std::auto_ptr<AnyPtr> instead. I don't think AnyVariable's should
behave
like pointers and share state when copied - just clone the pointed-to
object.
HTH,
Michiel Salters