The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference, 2nd Edition
by Nicolai M. Josuttis, Addison Wesley Longman, 2012
Copyright © 2012 by Pearson Education, Inc. and Nicolai M. Josuttis
#include <iostream>
#include <string>
#include <vector>
#include <memory>
using namespace std;
class Person : public enable_shared_from_this<Person> {
public:
string name;
shared_ptr<Person> mother;
shared_ptr<Person> father;
vector<weak_ptr<Person>> kids; // weak pointer !!!
Person (const string& n)
: name(n) {
}
void setParentsAndTheirKids (shared_ptr<Person> m = nullptr,
shared_ptr<Person> f = nullptr) {
mother = m;
father = f;
if (m != nullptr) {
m->kids.push_back(shared_from_this());
}
if (f != nullptr) {
f->kids.push_back(shared_from_this());
}
}
~Person() {
cout << "delete " << name << endl;
}
};
shared_ptr<Person> initFamily (const string& name)
{
shared_ptr<Person> mom(new Person(name+"'s mom"));
shared_ptr<Person> dad(new Person(name+"'s dad"));
shared_ptr<Person> kid(new Person(name));
kid->setParentsAndTheirKids(mom,dad);
return kid;
}
int main()
{
shared_ptr<Person> p = initFamily("nico");
cout << "nico's family exists" << endl;
cout << "- nico is shared " << p.use_count() << " times" << endl;
cout << "- name of 1st kid of nico's mom: "
<< p->mother->kids[0].lock()->name << endl;
p = initFamily("jim");
cout << "jim's family exists" << endl;
}