#include <iostream> struct hoge { }; int main(){ std::unique_ptr<hoge> a; std::cout << a << std::endl; // a is empty a.reset(new hoge()); std::cout << a << std::endl; // a is not empty std::unique_ptr<hoge> b; std::cout << b << std::endl; // b is empty b = std::move(a); // b = a; won't work. // error: object of type ... cannot be assigned because its copy assignment operator is implicitly deleted // note: copy assignment operator is implicitly deleted because ... has a user-declared move constructor std::cout << a << std::endl; // a is empty std::cout << b << std::endl; // b is not empty }