[Αμετάφραστο] Combining Smart Pointers

Smart pointers might seem limited, but they can make some very powerful combinations.

Rc<Vec<Foo>> - Allow the cloning of multiple smart pointers that can borrow the same vector of immutable data structures on the heap.

Rc<RefCell<Foo>> - Allow multiple smart pointers the ability to borrow mutably/immutably the same struct Foo

Arc<Mutex<Foo>> - Allow multiple smart pointers the ability to lock temporary mutable/immutable borrows in a CPU thread exclusive manner.

Memory detail:

• You'll notice a theme with many of these combinations. The use of an immutable data type (possibly owned by multiple smart pointers) to modify internal data. This is referred to as the "interior mutability" pattern in Rust. It is a pattern that lets us bend the rules of memory usage at runtime with the same level of safety as Rust's compile-time checks.