Will ObjC setter automatically copy a C++ object passed as a parameter when get called?

Question

I recently read about a std::unique_ptr as a @property in objective c and the suggestion to store a unique_ptr in ObjC as a property is as following:

-(void) setPtr:(std::unique_ptr<MyClass>)ptr {
    _ptr = std::move(ptr);
}

My question is in ObjC, does the parameter get copied in this case? Because if that happens, unique_ptr shall never be declared as a property right?

Answer 1

I would not expect that code to compile as ptr is being passed by value there.

Better would be:

-(void) setPtr:(std::unique_ptr<MyClass>) &&ptr {
    _ptr = std::move(ptr);
}

---

Edit: Thinking about it, that might not compile either. I don't know if Objective_C understands passing parameters by reference, rvalue or otherwise. But if it doesn't, this should work:

-(void) setPtr:(std::unique_ptr<MyClass>) *ptr {
    _ptr = std::move(*ptr);
}