Originally Posted by
CornedBee
Nothing, really. You just have to remember that, once you have a reference member, several things happen. First, you don't get a generated copy assignment operator. Second, the class is no longer a POD, even if it would have been otherwise. Third, if the reference can refer to different objects in different instances, you cannot implement a reliable assignment operator or a reliable swap, because the functions would have to fail for objects coming - in your example - from different worlds. Built-in xenophobia ;)
So when I said that references make poor class members, I was referring to the fact that having a reference member affects the design of the class.