C++的右值引用
右值引用主要用于移动语义(Move semantics)和完美转发(Perfect forwarding) Move semantics Move semantics能转移一个对象到另一个对象上，避免不必要的内存拷贝，被拷贝对象不能在其它地方被引用。要实现Move semantics只要给类定义移动构造函数和可选的移动赋值操作： class Memory { public: Memory(Memory&& other) noexcept { _data = other._data; _length = other._length; other._data = nullptr; other._length = 0; } Memory& operator=(Memory&& other) noexcept { if (this != &other) { delete[] _data; _data = other._data; _length = other._length; other._data = nullptr; other._length = 0; } return *this; } private: void *_data{nullptr}; int _length{0}; } Perfect forwarding Perfect forwarding主要为了减少重载函数，主要是泛型函数用引用类型作为参数。 struct W { W(int&, int&) {} }; struct Z { Z(const int&, const int&) {} }; template <typename T, typename A1, typename A2> T* factory(A1& a1, A2& a2) { return new T(a1, a2); } int a = 4, b = 5; W* pw = factory<W>(a, b); // OK Z* pz = factory<Z>(2, 2); // Valid cause 2 is right value 把上面的泛型函数参数改成右值引用就能解决这个问题： template <typename T, typename A1, typename A2> T* factory(A1&& a1, A2&& a2) { return new T(std::forward<A1>(a1), std::forward<A2>(a2)); } Z* pz = factory<Z>(2, 2); // OK References: https://learn.microsoft.com/en-us/cpp/cpp/rvalue-reference-declarator-amp-amp?view=msvc-170