Question

I came across people passing data objects as:

declaration:

DataObject * data = 0;

calling it as:

SomeMethod( data );

definition of Somethod:

void SomeMethod(SomeObject * & object)

My obvious question is, when and why do you have to do this (& *)?
Is it passing the pointer as reference?

Answer 1

Yes, exactly!

So, not only can your function SomeMethod refer to the same data as the caller, but it can actually change what the caller points to!

int main() {
   SomeObject* data = new SomeObject(1);
   cout << data << " -> " << *data;  // "0xfffee314 -> 1"

   SomeMethod(data);
   cout << data << " -> " << *data;  // "0xeee32435 -> 2"
}

void SomeMethod(SomeObject*& object) {
   delete object;
   object = new SomeObject(2);
}