Do we need to always pass an object to a function by reference?

Question

In the composition part 2 we pass the object birthday to the constructor as it is(not by reference) but in keyword friend topic we pass the object by reference and it's written in Note that we should pass the object by reference can we pass it only by reference or directly or do we have to do it for non-member functions only which we define as object.

Answer 1

Hey Abhishek ,
if you post question with code then that would be good to analyse ..