The ref pattern - Rust By Example
Description: A description

# The ref pattern

When doing pattern matching or destructuring via the `let` binding, the `ref` keyword can be used to take references to the fields of a struct/tuple. The example below shows a few instances where this can be useful:

    #[derive(Clone, Copy)]
    struct Point { x: i32, y: i32 }

    fn main() {
        let c = 'Q';

        // A `ref` borrow on the left side of an assignment is equivalent to
        // an `&` borrow on the right side.
        let ref ref_c1 = c;
        let ref_c2 = &c;

        println!("ref_c1 equals ref_c2: {}", *ref_c1 == *ref_c2);

        let point = Point { x: 0, y: 0 };

        // `ref` is also valid when destructuring a struct.
        let _copy_of_x = {
            // `ref_to_x` is a reference to the `x` field of `point`.
            let Point { x: ref ref_to_x, y: _ } = point;

            // Return a copy of the `x` field of `point`.
            *ref_to_x
        };

        // A mutable copy of `point`
        let mut mutable_point = point;

        {
            // `ref` can be paired with `mut` to take mutable references.
            let Point { x: _, y: ref mut mut_ref_to_y } = mutable_point;

            // Mutate the `y` field of `mutable_point` via a mutable reference.
            *mut_ref_to_y = 1;
        }

        println!("point is ({}, {})", point.x, point.y);
        println!("mutable_point is ({}, {})", mutable_point.x, mutable_point.y);

        // A mutable tuple that includes a pointer
        let mut mutable_tuple = (Box::new(5u32), 3u32);

        {
            // Destructure `mutable_tuple` to change the value of `last`.
            let (_, ref mut last) = mutable_tuple;
            *last = 2u32;
        }

        println!("tuple is {:?}", mutable_tuple);
    }