智能指针weak_ptr解决循环依赖问题

#include <iostream>  
#include <memory>  

class Woman;
class Man{
private:
    std::weak_ptr<Woman> _wife;
    //std::shared_ptr<Woman> _wife;  
public:
    void setWife(std::shared_ptr<Woman> &woman){
        _wife = woman;
    }

    void doSomthing(){
        if (_wife.lock()){
        }
    }

    ~Man(){
        std::cout << "kill man\n";
    }
};

class Woman{
private:
    //std::weak_ptr<Man> _husband;  
    std::shared_ptr<Man> _husband;
public:
    void setHusband(std::shared_ptr<Man> &man){
        _husband = man;
    }
    ~Woman(){
        std::cout << "kill woman\n";
    }
};

int main()
{
    std::shared_ptr<Man> m(new Man());
    std::shared_ptr<Woman> w(new Woman());

    if (m && w) 
    {
        m->setWife(w);
        w->setHusband(m);
    }
    return 0;
}