Are references and pointers equal with regards to polymorphism?

Question

I always think of having to use pointers for polymorphism. Using the canonical example:

DrawEngine::render(Shape *shape)
{
    shape->draw();
    shape-&g         


        

Answer 1

Regarding dynamic_cast, a failed cast produces a nullpointer with pointers, and results in a throw of a bad_cast (IIRC) exception with references.

One reason is that there's no such thing as a valid null-reference.

And possibly another reason (but it could just be an unintentionally useful emergent feature) is that sometimes one needs the exception and sometimes one needs the easy-to-check nullpointer, and no matter whether you have a reference or pointer at hand it takes at most a dereferencing or address operator to obtain the behavior you want.

Cheers & hth.,

Answer 2

Pointers help in other ways as well. Like passing a string and accepting it as char* parameter in a function.

Consider the old example of reversing a string in place:

void reversestring(char* myString)
{
int firstPos=0;
int lastPos=myString.length - 1;
while (firstPos < lastPos)
{
  char temp=myString[firstPos];
  myString[firstPos]=myString[lastPos];
  myString[lastPos]=temp;
  firstPos++;
  lastPos--;
}
}

Writing code for string manipulation like these using references won't be that simple.

Answer 3

With regard to polymorphism, references work just like pointers.