How do I pass a unique_ptr argument to a constructor or a function?

Question

<!-- language-all: lang-cpp --> I'm new to move semantics in C++11 and I don't know very well how to handle `unique_ptr` parameters in constructors or functions. Consider this class referencing itself: #include <memory> class Base { public: typedef unique_ptr<Base> UPtr; Base(){} Base(Base::UPtr n):next(std::move(n)){} virtual ~Base(){} void setNext(Base::UPtr n) { next = std::move(n); } protected : Base::UPtr next; }; Is this how I should write functions taking `unique_ptr` arguments? And do I need to use `std::move` in the calling code? Base::UPtr b1; Base::UPtr b2(new Base()); b1->setNext(b2); //should I write b1->setNext(std::move(b2)); instead?

Answer 1

Depending on the scenario, you either want to pass a std::unqiue_ptr by reference or use std::move.

If you want the pointer to remain valid in the calling code, it should be passed by reference.

If you are okay to "give up" the pointer in the calling code, pass by value and use std::move.