How to Use the Deref and DerefMut Traits in Rust

Implement Deref to treat a custom type like a reference and DerefMut to allow mutable access through the dereference operator.

use std::ops::{Deref, DerefMut};

struct MyBox<T>(T);

impl<T> MyBox<T> {
    fn new(x: T) -> MyBox<T> { MyBox(x) }
}

impl<T> Deref for MyBox<T> {
    type Target = T;
    fn deref(&self) -> &Self::Target { &self.0 }
}

impl<T> DerefMut for MyBox<T> {
    fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 }
}

fn main() {
    let mut x = MyBox::new(5);
    println!("{}", *x); // Uses Deref
    *x = 10; // Uses DerefMut
    println!("{}", *x);
}

These traits let you write custom data structures that act like standard references. Deref allows you to read the inner value using the * operator, while DerefMut lets you change it. Think of it as giving your custom wrapper a universal key that fits into any lock expecting a standard reference.