Re: update object

Is it possible to "update" an object in this sense?
I have an object of Base class and pointers to this object. Finally I
would like to replace this object by an object of Derived class and all
pointer contain the address of the new object. Here is an unsucsessful
attempt to do it.

#include <iostream>
using namespace std;

class Base {
public:
 Base();
 virtual void speak();
};

class Derived: public Base {
public:
 Derived();
 virtual void speak();
};

Base::Base() {
}

void Base::speak() {
 cout << "I am an object of class Base" << '\n';
}

Derived::Derived() {
}

void Derived::speak() {
 cout << "I am an object of class Derived" << '\n';
}

int main () {
 Derived objD;
 Base* p1 = new Base();
 Base* p2 = p1;

 Derived* z = new Derived; //new class

 *p1 = *z; //it is assign and the result is a Base class

 p1->speak();//does not work, it is still Base class

 return 0;
}