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.
#![feature(box_syntax)]
#![feature(box_patterns)]
#[derive(Copy)]
struct Point { x: i32, y: i32 }
fn main() {
let point = Point { x: 0, y: 0 };
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);
let mut tuple = (box 5u32, 3u32);
{
// `ref` can also be paired with `box` to take a mutable reference to
// the data contained in the box
let (box ref mut i, _) = tuple;
*i = 3;
}
println!("tuple is {:?}", tuple);
}