Question

class A {...}  
class B : public A {...}  
class C : public A {...}  
void M(A* a) {
  A* aa = new B(* a)
  ...
}  
int main()  
{  
  B b = new B();  
  M(b);  
  ...
}  

So what I want is to do is call the copy constructor of the object (“a”) that is passed to M without having to know whether it’s of type B or C etc (instead of the “new B( a)” as above).

Of course, I can use dynamic cast and check for a null ptr etc or use typeid, but there must be an easier way?

Thanks in advance.

Answer 1

---

One way to get the same effect would be to use the clone() pattern. Give class A a virtual function that copies it, overriding that function in each subclass. Pass an instance of A to your function by reference, and then clone it within that function. A bit messy, but works.