c++ - 为什么 C2662 错误不适用于对 std::unique_ptr对象的 const 引用？

Answer 1

const std::unique_ptr<B>类似于B* const，即指向可变对象的不可变指针B-not const B*，指向不可变对象的可变指针B。如果你想从unique_ptr版本中得到同样的错误，你需要写std::unique_ptr<const B>. 实际上，您正在返回unique_ptrbyconst引用，但B它所引用的不是const。

Answer 2

You are returning a const reference from your getB() method. You cannot change the address to which a const reference points. Yet calling get() on the returned object would give you the pointer. That is not a good thing to try!