C++ vector: upcasting subclasses to a superclass

Question

How to upcast the vectors in my subclasses to superclass so that I can just use one pointer to modify and browse through the objects in the vectors? Thank you in advance!

class S { ... };

class A : public S { ... };
class B : public S { ... };
class C : public S { ... };

int main(){
  vector<A> aVec;
  A a;
  a.addList(aVec, ...some attributes...); //add objects into aVec using a function in class S
  a.addList(aVec, ...some attributes...);

  vector<B> bVec;
  B b;
  b.addList(bVec, ...some attributes...); //add objects into bVec using a function in class S

  vector<C> cVec;
  C c;
  c.addList(cVec, ...some attributes...); //add objects into cVec using a function in class S


}

Answer 1

One way to do this is to have a std::vector<std::unique_ptr<S>> and create your objects like std::unique_ptr<S>(new A) and store them in the vector as appropriate.

Using unique_ptrs not just raw pointers will ensure your objects are appropriately destructed just like they would be if they were directly stored in the vector.