member variable as a reference

Question

What is the advantage of declaring a member variable as a reference? I saw people doing that, and can't understand why.

Answer 1

One useful case is when you don't have access to the constructor of that object, yet don't want to work with indirection through a pointer. For example, if a class A does not have a public constructor and your class wants to accept an A instance in its constructor, you would want to store a A&. This also guarantees that the reference is initialized.

Answer 2

A member reference is useful when you need to have access to another object, without copying it.

Unlike a pointer, a reference cannot be changed (accidentally) so it always refers to the same object.