Using a weak_ptr to hold weak references to smart pointers.

Introduction

weak_ptr gets a pointer to a shared object temporarily when you need it as the shared object exists.

Demo Code

#include <iostream>
#include <memory>
#include <string>
using namespace std;

class MyClass/*  ww  w.j a  v a 2s  .  co  m*/
{
private:
    string m_Name;
    int m_Value;
public:
    MyClass(const string& name, int value) : m_Name{ name } , m_Value{ value }
    {
        cout << "Constructing!" << endl;
    }

    ~MyClass()
    {
        cout << "Destructing!" << endl;
    }

    const string& GetName() const
    {
        return m_Name;
    }

    int GetValue() const
    {
        return m_Value;
    }
};

using MySharedPtr = shared_ptr<MyClass>;
using MyWeakPtr = weak_ptr<MyClass>;

auto PassSharedPtr(MySharedPtr ptr)
{
    cout << "In Function Name: " << ptr->GetName() << endl;
    return ptr;
}

int main()
{
    MyWeakPtr weakPtr;
    {
        auto sharedPointer = make_shared<MyClass>("MyClass", 10);
        weakPtr = sharedPointer;

        {
            auto newSharedPointer = PassSharedPtr(sharedPointer);
            if (sharedPointer)
            {
                cout << "First Object Name: " << sharedPointer->GetName() << endl;
            }

            cout << "Second Object Name: " << newSharedPointer->GetName() << endl;
            auto sharedFromWeak1 = weakPtr.lock();
            if (sharedFromWeak1)
            {
                cout << "Name From Weak1: " << sharedFromWeak1->GetName() << endl;
            }
        }
    }

    auto sharedFromWeak2 = weakPtr.lock();
    if (!sharedFromWeak2)
    {
        cout << "Shared Pointer Out Of Scope!" << endl;
    }

    return 0;
}

Using a weak_ptr to hold weak references to smart pointers. - C++ Data Type

Introduction

Demo Code

Result

Related Tutorials