I'd create a couple of function templates, static_unique_ptr_cast
and dynamic_unique_ptr_cast
. Use the former in cases where you're absolutely certain the pointer is actually a Derived *
, otherwise use the latter.
template<typename Derived, typename Base, typename Del>
std::unique_ptr<Derived, Del>
static_unique_ptr_cast( std::unique_ptr<Base, Del>&& p )
{
auto d = static_cast<Derived *>(p.release());
return std::unique_ptr<Derived, Del>(d, std::move(p.get_deleter()));
}
template<typename Derived, typename Base, typename Del>
std::unique_ptr<Derived, Del>
dynamic_unique_ptr_cast( std::unique_ptr<Base, Del>&& p )
{
if(Derived *result = dynamic_cast<Derived *>(p.get())) {
p.release();
return std::unique_ptr<Derived, Del>(result, std::move(p.get_deleter()));
}
return std::unique_ptr<Derived, Del>(nullptr, p.get_deleter());
}
The functions are taking an rvalue reference to ensure that you're not pulling the rug out from underneath the caller's feet by stealing the unique_ptr
passed to you.