Is it possible to change a C++ object's class after instantiation?

Question

I have a bunch of classes which all inherit the same attributes from a common base class. The base class implements some virtual functions that work in general cases, whilst eac

Answer 1

you cannot change to the type of an object after instantiation, as you can see in your example you have a pointer to a Base class (of type base class) so this type is stuck to it until the end.

• the base pointer can point to upper or down object doesn't mean changed its type:

  Base* ptrBase; // pointer to base class (type)
  ptrBase = new Derived; // pointer of type base class `points to an object of derived class`
  
  Base theBase;
  ptrBase = &theBase; // not *ptrBase = theDerived: Base of type Base class points to base Object.
  

• pointers are much strong, flexible, powerful as much dangerous so you should handle them cautiously.

in your example I can write:

Base* object; // pointer to base class just declared to point to garbage
Base bObject; // object of class Base
*object = bObject; // as you did in your code

above it's a disaster assigning value to un-allocated pointer. the program will crash.

in your example you escaped the crash through the memory which was allocated at first:

object = new Derived;

it's never good idea to assign a value and not address of a subclass object to base class. however in built-in you can but consider this example:

int* pInt = NULL;

int* ptrC = new int[1];
ptrC[0] = 1;

pInt = ptrC;

for(int i = 0; i < 1; i++)
    cout << pInt[i] << ", ";
cout << endl;

int* ptrD = new int[3];
ptrD[0] = 5;
ptrD[1] = 7;
ptrD[2] = 77;

*pInt = *ptrD; // copying values of ptrD to a pointer which point to an array of only one element!
// the correct way:
// pInt = ptrD;

for(int i = 0; i < 3; i++)
    cout << pInt[i] << ", ";
cout << endl;

so the result as not as you guess.