std::unique_ptr with derived class

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If they are polymorphic types and you only need a pointer to the derived type use dynamic_cast:

Derived *derivedPointer = dynamic_cast<Derived*>(basePointer.get());

If they are not polymorphic types only need a pointer to the derived type use static_cast and hope for the best:

Derived *derivedPointer = static_cast<Derived*>(basePointer.get());

If you need to convert a unique_ptr containing a polymorphic type:

Derived *tmp = dynamic_cast<Derived*>(basePointer.get());
std::unique_ptr<Derived> derivedPointer;
if(tmp != nullptr)
{
    basePointer.release();
    derivedPointer.reset(tmp);
}

If you need to convert unique_ptr containing a non-polymorphic type:

std::unique_ptr<Derived>
    derivedPointer(static_cast<Derived*>(basePointer.release()));

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