How can I make static_cast from unique_ptr

Question

I have the following code, how to cast correctly from unique_ptr to base class?:

class MagEventNotifierAndSupplier : public CSubject,
    IMagneticData
{
public:
//implement
}
unique_ptr<MagEventNotifierAndSupplier> m_MagEventNotifierAndSupplier;
m_MagEventNotifierAndSupplier = make_unique<MagEventNotifierAndSupplier>("test");
IMagneticData* data= static_cast<IMagneticData*>(&m_MagEventNotifierAndSupplier);// invalid cast

Have you tried: IMagenticData* dynamic_cast (m_MagEventNotifierAndSupplier.get()) — Omid CompSCI, Jul 10 '20 at 21:12
Why dynamic_cast? It's for casting base pointer to a derived one. — Alexander Dyagilev, Jul 10 '20 at 21:14
You should be able to get pointer to a base class easily without any explicit casting. Just use get() method of the unique_ptr class. — Alexander Dyagilev, Jul 10 '20 at 21:15
1. IMagneticData* data= m_MagEventNotifierAndSupplier.get(); 2. Switch to public inheritance, i.e. class MagEventNotifierAndSupplier : public CSubject, public IMagneticData. — Alexander Dyagilev, Jul 10 '20 at 21:19

score 1 · Answer 1 · answered Jul 10 '20 at 22:59

You can't static_cast a unique_ptr* pointer to a IMagneticData* pointer, as they are unrelated types.

You don't need a cast at all. Since MagEventNotifierAndSupplier derives from IMagneticData, a MagEventNotifierAndSupplier* pointer can be assigned directly to an IMagneticData* pointer without casting.

You can get a MagEventNotifierAndSupplier* pointer from a std::unique_ptr<MagEventNotifierAndSupplier> object via its get() method, eg:

class MagEventNotifierAndSupplier : public CSubject, public IMagneticData
{
public:
    //implement
};

auto m_MagEventNotifierAndSupplier = std::make_unique<MagEventNotifierAndSupplier>("test");
IMagneticData* data = m_MagEventNotifierAndSupplier.get();

How can I make static_cast from unique_ptr

1 Answers1