struct Basis {virtual ~Basis(){}  };
struct Derived : public Basis {};

int main()
{
    Basis* ptr = new Derived();
    Derived* ptrDerived = dynamic_cast<Derived*>(ptr);
}

so und wie funzt das analog mit:

boost::shared_ptr<Basis> ptr(new Derived);
   boost::shared_ptr<Derived> ptrDerived = dynamic_cast<Derived*>(ptr); //<-funzt natürlich nicht!  :rolleyes:

gruß, SirAnn

Edit: Entweder shared_ptr::get() oder get_pointer(shared_ptr&)

Aber für dich das richtige ist wohl eher:

dynamic_pointer_cast

template<class T, class U>
shared_ptr<T> dynamic_pointer_cast(shared_ptr<U> const & r);
Requires: The expression dynamic_cast<T*>(r.get()) must be well-formed and its behavior defined.

Returns:

When dynamic_cast<T*>(r.get()) returns a nonzero value, a shared_ptr<T> object that stores a copy of it and shares ownership with r;
Otherwise, an empty shared_ptr<T> object.
Throws: nothing.

Notes: the seemingly equivalent expression

shared_ptr<T>(dynamic_cast<T*>(r.get()))

will eventually result in undefined behavior, attempting to delete the same object twice.

Von http://www.boost.org/libs/smart_ptr/shared_ptr.htm#Members

1000 dank. das haut natürlich hin...

aber der vollständigkeit halber:

so geht's:

boost::shared_ptr<Derived> ptrDerived = boost::dynamic_pointer_cast<Derived>(ptr);

wie gewohnt ist eben ptr.get()==NULL, wenne s nicht geklappt hat bzw !ptr==true