Smart Pointers Pattern

Patterns สำหรับ smart pointer types ใน Rust ที่ manage memory และ ownership

1. Box - Heap Allocation

Box<T> allocate data บน heap แทน stack สำหรับ recursive types และ trait objects

Using Box

fn main() {
    // Simple heap allocation
    let boxed = Box::new(42);
    println!("Boxed: {}", *boxed);

    // For recursive types
    #[derive(Debug)]
    enum List {
        Cons(i32, Box<List>),
        Nil,
    }

    let list = List::Cons(1,
        Box::new(List::Cons(2,
            Box::new(List::Cons(3,
                Box::new(List::Nil))))));

    println!("List: {:?}", list);

    // For trait objects
    trait Animal {
        fn speak(&self);
    }

    struct Dog;
    impl Animal for Dog {
        fn speak(&self) { println!("Woof!"); }
    }

    let animal: Box<dyn Animal> = Box::new(Dog);
    animal.speak();

    // Box::leak for static lifetime
    let static_str: &'static str = Box::leak(String::from("forever").into_boxed_str());
    println!("Static: {}", static_str);
}