test_weaker_ptr.cpp

#include <iostream>
#include <memory> // for std::shared_ptr and std::weak_ptr
#include <string>
 
class Person
{
	std::string m_name;
	std::weak_ptr<Person> m_partner; // note: This is now a std::weak_ptr
 
public:
 
	Person(const std::string &name) : m_name(name)
	{
		std::cout << m_name << " created\n";
	}
	~Person()
	{
		std::cout << m_name << " destroyed\n";
	}
 
	friend bool partnerUp(std::shared_ptr<Person> &p1, std::shared_ptr<Person> &p2)
	{
		if (!p1 || !p2)
			return false;
 
		p1->m_partner = p2;
		p2->m_partner = p1;
 
		std::cout << p1->m_name << " is now partnered with " << p2->m_name << "\n";
 
		return true;
	}
 
    // This is safe, for if m_partner's managed resource is not available, then m_partner.lock will return nullptr which is 
    // a fail-safe method to prevent accessing invalid pointer.
	const std::shared_ptr<Person> getPartner() const { return m_partner.lock(); } // use lock() to convert weak_ptr to shared_ptr
	const std::string& getName() const { return m_name; }
};
 
int main()
{
	auto lucy = std::make_shared<Person>("Lucy");
	auto ricky = std::make_shared<Person>("Ricky");
 
	partnerUp(lucy, ricky);
 
	auto partner = ricky->getPartner(); // get shared_ptr to Ricky's partner
	std::cout << ricky->getName() << "'s partner is: " << partner->getName() << '\n';
 
	return 0;
}