Question

Can someone please give some examples where pass by reference is preferred over pass by pointer.

Basically both offer the same functionality but I want to know where pass by reference becomes mandatory.

Also, please suggest how to decide to use either of the two.

Please suggest with some basic examples.

Answer 1

Copy constructor and Assignment operator.

struct A {
  ...
  A(const A& copy);
  A& operator = (const A& copy);
};

These are mandatory situations. Apart from these there can be other situations also (e.g. overloading other operators like +, <, > and so on).

Also, please suggest how to decide to use either of the two.

I prefer references (more C++ style) at most of the places and if a reference can’t be used, I tend to use pointers (more C style).
Reference are somewhat analogical representation of a const pointer; i.e. A& is similar as A* const. Thus they provide some in-built safety against overwriting the location accidently.