How can I use the insertion operator with polymophism [duplicate] - c++

Question

This question already has answers here:
Overriding of operator<< in c++
(2 answers)
Closed 7 years ago.
I want to implement a composite pattern where I can print the contents using std::cout
When I print, the base class insertion operator (operator<<) is used instead of the most derived type. How can I cause the most derived type operator to be used?
Example:
#include <iostream>
#include <memory>
using namespace std;
class Base {
int i;
public:
Base(int _i) : i(_i) {}
virtual ~Base() {}
friend inline ostream& operator<<(ostream& os, Base& value) { return os << "i: " << value.i; }
friend inline ostream& operator<<(ostream& os, shared_ptr<Base> value) { return os << "i: " << value->i; }
};
class Derived : public Base {
int x;
public:
Derived(int _x) : Base(2*_x), x(_x) {}
friend inline ostream& operator<<(ostream& os, Derived& value) { return os << "x: " << value.x; }
friend inline ostream& operator<<(ostream& os, shared_ptr<Derived> value) { return os << "x: " << value->x; }
};
int main () {
Base* a = new Base(1);
Derived* d = new Derived(6);
Base* b = new Derived(7);
shared_ptr<Base> ba = make_shared<Base>(3);
shared_ptr<Derived> de = make_shared<Derived>(4);
shared_ptr<Base> bd = make_shared<Derived>(5);
cout << "a is: " << a << endl;
cout << "*a is: " << *a << endl;
cout << "d is: " << d << endl;
cout << "*d is: " << *d << endl;
cout << "b is: " << b << endl;
cout << "*b is: " << *b << endl << endl;
cout << "ba is: " << ba << endl;
cout << "*ba is: " << *ba << endl;
cout << "de is: " << de << endl;
cout << "*de is: " << *de << endl;
cout << "bd is: " << bd << endl;
cout << "*bd is: " << *bd << endl;
delete a;
delete d;
delete b;
return 0;
}
live code
This spits out
a is: 0x1fe2bb0
*a is: i: 1
d is: 0x1fe2bd0
*d is: x: 6
b is: 0x1fe2bf0
*b is: i: 14
ba is: i: 3
*ba is: i: 3
de is: x: 4
*de is: x: 4
bd is: i: 10
*bd is: i: 10
But I would like to see *b print 7 and bd print 5 (ie. use the Derived class' insertion operator)

Answer 1

Ok, after searching a lot more, I found this answer. After smacking my head and saying 'of course', I summarize:
Don't overload the insertion operator since you can't make it virtual (it's not a member function), instead declare a virtual function in the base class that is overridden in the child classes. The insertion operator uses this function:
class Base {
...
friend inline ostream& operator<<(ostream& os, shared_ptr<Base> value) { return value->display(os, value); }
virtual ostream& display(ostream& os) { os << "i: " << i << endl; }
};
class Derived : public Base {
...
ostream& display(ostream& os) { os << "x: " << x << endl; }
};
live code