constness for reference class members

Question

I have a couple of classes one of which keeps reference to the object of other:

class Inner {};

class Outer {
    Inner & in;

public:
    Outer(Inner & in) : in(in) {}
};

What if I have to create Outer object from const reference to Inner? Am I have to write specific class, say OuterConst, for this?

UPD: Any neat solutions using templates? In order to avoid duplication of code in OuterConst class.

UPD2: when Inner comes without const it should be modifiable (so I can't just add const to Inner member in current implementation of Outer).

Answer 1

What if I have to create Outer object from const reference to Inner?

Well, you can't. That's pretty much it. If Outer only needs to call const member functions of Inner, then make it a const reference- else, your class depends on a mutable Inner object and you should not create an Outer object from a const reference.