Course Content

C++ Smart Pointers

1. Introduction to Smart Pointers

Understanding Pointers Dynamic memory allocation The Need For Smart Pointers

2. Unique Pointers

Introduction to Unique Pointers Moving Unique Pointers Application For Unique Pointers Passing Around Unique Pointers Methods of a Unique Pointer

3. Shared Pointers

Introduction to Shared Pointers Creating and Sharing Shared Pointers Circular References and Shared Pointers

4. Weak Pointers

Introduction to Weak Pointers Creating And Using Weak Pointers Breaking Circular References With Weak Pointers Important Weak Pointer Functions

5. Advanced topics

Providing Custom Deleters For Smart Pointers Performance Considerations With Smart Pointers Overview Shared vs Unique vs Weak Pointers

Creating And Using Weak Pointers

Creating Weak Pointers

You should typically create a std::weak_ptr from an existing std::shared_ptr. This ensures that the weak pointer observes an object that is already managed by at least one shared pointer.

creating_weak_pointer


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std::shared_ptr<int> p_shared = std::make_shared<int>(42);
std::weak_ptr<int> p_weak(sharedPtr);

The std::weak_ptr p_weak is constructed from an existing std::shared_ptr p_shared. This means p_weak does not increase the reference count of p_shared but instead observes the same managed object. The validity of p_weak depends on p_shared; if all std::shared_ptr instances managing the object are destroyed, p_weak expires and can no longer be used to access the object directly.

Using Weak Pointers

To access an object managed by a std::weak_ptr, you must first convert it to a std::shared_ptr using lock(). This method checks whether the object is still alive and returns a std::shared_ptr to it and otherwise, it returns an empty std::shared_ptr.

Locking a weak pointer prevents the object from being destroyed while in use. Since std::weak_ptr does not contribute to the reference count, directly accessing the object would risk using a destroyed instance. Converting it to a std::shared_ptr increases the reference count, ensuring the object remains valid during use.

converting


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auto locked_shared = p_weak.lock();
if (locked_shared)
    // The object is alive, and you can use lockedSharedPtr to access it.
else
    // The object has been deallocated, and lockedSharedPtr is empty.

Task

Swipe to start coding

Complete the following code to create a std::weak_ptr from a std::shared_ptr, convert it back to a std::shared_ptr, and safely access the value of the managed object.

Solution

solution

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Section 4. Chapter 2

Creating And Using Weak Pointers

Creating Weak Pointers

You should typically create a std::weak_ptr from an existing std::shared_ptr. This ensures that the weak pointer observes an object that is already managed by at least one shared pointer.

creating_weak_pointer


              12
            
std::shared_ptr<int> p_shared = std::make_shared<int>(42);
std::weak_ptr<int> p_weak(sharedPtr);

Using Weak Pointers

converting


              12345
            
auto locked_shared = p_weak.lock();
if (locked_shared)
    // The object is alive, and you can use lockedSharedPtr to access it.
else
    // The object has been deallocated, and lockedSharedPtr is empty.

Task

Swipe to start coding

Complete the following code to create a std::weak_ptr from a std::shared_ptr, convert it back to a std::shared_ptr, and safely access the value of the managed object.

Solution

solution

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Section 4. Chapter 2

Switch to desktop for real-world practiceContinue from where you are using one of the options below