Smart Pointers
Box<T>, Rc<T>, Arc<T>, RefCell<T>, interior mutability, Deref, Drop traits
1What is the primary use case for Box<T> in Rust?
What is the primary use case for Box<T> in Rust?
답변
Box<T> allocates data on the heap instead of the stack. This is useful for types with unknown size at compile time (recursive types), transferring ownership of large data without copying, or creating trait objects. The Box pointer itself has a fixed size on the stack.
2How to define a recursive type like a linked list in Rust?
How to define a recursive type like a linked list in Rust?
답변
A direct recursive type like enum List { Cons(i32, List), Nil } does not compile because the compiler cannot determine the size. Using Box<List> creates an indirection with a fixed size (pointer), allowing the compiler to calculate the type's size.
3What is the main difference between Rc<T> and Arc<T>?
What is the main difference between Rc<T> and Arc<T>?
답변
Rc (Reference Counted) uses a non-atomic reference counter, making it more performant but limited to a single thread. Arc (Atomically Reference Counted) uses atomic operations for the counter, enabling sharing across threads but with a slight performance overhead.
What does the Deref trait enable in Rust?
What is interior mutability in Rust?
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