A Static Counter Inside operator<<

1#include <iostream>
2#include <string>
3using namespace std;
4 
5class Ticket {
6    string m_event;
7public:
8    Ticket(const string& event) : m_event(event) {}
9    friend ostream& operator<<(ostream& os, const Ticket& t);
10};
11 
12ostream& operator<<(ostream& os, const Ticket& t) {
13    static int calls = 0;
14    calls++;
15    os << "Print " << calls << ": " << t.m_event;
16    return os;
17}
18 
19int main() {
20    Ticket a("Jazz"), b("Rock");
21    cout << a << endl;
22    cout << a << endl;
23    Ticket c = b;
24    cout << c << " | " << b << endl;
25    return 0;
26}