When to Use Shared Pointers

Shared pointers (std::shared_ptr) should be used when you need multiple ownership semantics for a resource, i.e., when you want multiple pointers to share ownership of an object.

Here are some specific situations where shared pointers are often used:

1. Sharing resources: If you have a resource that needs to be shared across multiple parts of your code, and you want the resource to be automatically cleaned up when it's no longer needed, a shared pointer can be a good choice.
2. Complex data structures: In data structures like graphs or trees, nodes might be referenced from multiple places. If you want the nodes to be automatically deleted when they're no longer needed, shared pointers can be useful. However, you need to be careful to avoid cyclic references.
3. Caching: If you're implementing a cache, you might use shared pointers to manage the cached objects. When an object is no longer in the cache, and no other part of the code is using it, it will be automatically deleted.
4. Asynchronous operations: If you're spawning asynchronous operations that need to access a resource, you can pass them shared pointers to ensure the resource lives as long as it's needed, without having to manually coordinate the resource's lifetime.
5. Polymorphic ownership: If you have a base class pointer that might point to objects of derived classes, and you want the pointed-to object to be deleted when all pointers to it are gone, shared pointers can handle this correctly (as long as the base class has a virtual destructor).

On the other hand, you should prefer unique pointers (std::unique_ptr) when you want express unique ownership, i.e., when only one pointer should own the resource at a time. This is often the case for resources that are tied to a specific scope or object.

Raw pointers should be used when you don't own the resource at all, i.e., when you're just borrowing a reference to an object that is owned by someone else.

In general, the choice between std::unique_ptr, std::shared_ptr, and raw pointers comes down to the ownership semantics you need:

• std::unique_ptr: Single ownership
• std::shared_ptr: Shared ownership
• Raw pointer: No ownership

By choosing the appropriate pointer type, you can make your code express your intentions more clearly and avoid potential issues like memory leaks or dangling pointers.