shared_ptr usage with reference counting in a map
#include <iostream>
#include <memory>
#include <unordered_map>
//example of using shared_ptr in C++
const std::shared_ptr<int> dummy;
int main() {
std::unordered_map<int, std::shared_ptr<int>> items;
std::shared_ptr<int> ip = std::make_shared<int>(8);
std::cout << "Use count:" << ip.use_count() << "\n";
std::shared_ptr<int> ip2 = ip;
std::cout << "Use count:" << ip.use_count() << "\n";
items.insert({3, ip});
items.insert({4, ip});
std::cout << "Use count:" << ip.use_count() << "\n";
items.erase(3);
std::cout << "Use count:" << ip.use_count() << "\n";
items[4] = dummy;
std::cout << "Use count:" << ip.use_count() << "\n";
}
/*
Use count:1
Use count:2
Use count:4
Use count:3
Use count:2
*/