Question

I have abstract class Managee and helper class Wrapper. Pointer to Managee used to construct Wrapper, then Wrapper will take ownership over Managee. I want to ensure that user will always allocate new Managee. Are rvalue-references suitable for this goal?

Wrapper definition:

...
Wrapper(Managee * && tmpptr);
Managee & GetManagee();
...

Wrapper usage:

Wrapper a(new ManageeA()); // ok;
Wrapper b(&a.GetManagee()); // error?    <-----

Answer 1

Rvalue-references don’t help, since &a.GetManagee() is an rvalue.
Why not take a std::unique_ptr?

Wrapper(std::unique_ptr<Managee> ptr)
  : member_ptr(std::move(ptr)) {}

Managee& GetManagee();

Usage:

Wrapper a(make_unique<Managee>(/*args*/));

For make_unique, see here.

The best solution, however, wouldn’t even allow the user to create a Managee‘s derived types on the stack – this can be done with a factory function (of course with std::unique_ptr) and making constructors private:

class SomeClass : public Managee{
public:
  static std::unique_ptr<SomeClass> create(){
    return make_unique<SomeClass>();
  }
private:
  SomeClass(){}
  // other ctors
};