Returning unique_ptr and preventing move

Exotic_Devel

I have a class that has a property of type std::unique_ptr. I am implementing the gets and sets methods of this class and I need that the unique_ptr that is returned by the get method cannot be moved, ie that the pointer cannot be moved with std::move.
How does this return have to be to guarantee this?

class Operator
{
	private:
		QString _name;
		QString _login;
		QString _passw;
		std::unique_ptr<Profile> _profile;

	public:
		Operator();
		Operator(const QString &name, const QString &login, const QString &passw,
						 std::unique_ptr<Profile> getProfile);
		QString getName() const;
		void setName(const QString &name);
		QString getLogin() const;
		void setLogin(const QString &login);
		QString getPassw() const;
		void setPassw(const QString &passw);
		std::unique_ptr<Profile> getProfile() const; //Should I return by reference, by value, by lvalue (&), rvalue (&&)?
		void setProfile(std::unique_ptr<Profile> profile);
};

kshegunov

@Exotic_Devel said in Returning unique_ptr and preventing move:

Profile * getProfile() const;

Is simplest. The owned object continues to live where it does, you just return the member. If you can be sure that Profile is always valid, you can even return Profile &.

fcarney

It looks like you can return smart pointers via RVO, but it might require C++17:
https://www.internalpointers.com/post/move-smart-pointers-and-out-functions-modern-c

The comments also mention using std::move(ptr) to return a smart pointer, but you seemed to indicate problems with that.

kshegunov

@fcarney said in Returning unique_ptr and preventing move:

The comments also mention using std::move(ptr) to return a smart pointer, but you seemed to indicate problems with that.

The typical problem being that returning the unique_ptr transfers ownership.

fcarney

@kshegunov said in Returning unique_ptr and preventing move:

The typical problem being that returning the unique_ptr transfers ownership.

I am confused then. I thought he had trouble doing this. I didnt understand that he didnt want it to move.