checking that shared pointers are working right when mtple objects are sharing one resource, even when the first goes out of scope

shared_pointer_test.cpp

//
//  main.cpp
//  test_simple
//
//  Created by Sean Wu on 4/10/19.
//  Copyright © 2019 Sean Wu. All rights reserved.
//

#include <memory>
#include <functional>
#include <iostream>
#include <vector>

class widget {
public:
    
    static int id;
    
    widget(std::shared_ptr<std::vector<int>> ptr) : my_p(ptr), myid(id++) {};
    
    std::shared_ptr<std::vector<int>> my_p;
    int myid;
    
};

int widget::id = 0;


int main(int argc, const char * argv[]) {
    
    std::vector<widget*> widgets;
    
    {
        auto deleter = [](std::vector<int>* vptr){
            std::cout << " --- deleting vptr at " << vptr << " --- \n";
            delete vptr;
        };
        
        std::shared_ptr<std::vector<int>> p(new std::vector<int>{1,2,3,4,5}, deleter);
        
        std::cout << " --- ref count: " << p.use_count() << " --- \n";
        
        widgets.emplace_back(new widget(p));
        std::cout << " --- ref count: " << p.use_count() << " --- \n";
        widgets.emplace_back(new widget(p));
        std::cout << " --- ref count: " << p.use_count() << " --- \n";
        widgets.emplace_back(new widget(p));
        std::cout << " --- ref count: " << p.use_count() << " --- \n";
    }
    
    for(auto& it : widgets){
        std::cout << "widget: id " << it->myid << " pointing to " << it->my_p << " and ref count " << it->my_p.use_count() << "\n";
    }
    
    delete widgets[0];
    delete widgets[1];
    delete widgets[2];
    
    return 0;
}