How can I unpack (destructure) elements from a vector?

Question

I am currently doing the following:

let line_parts = line.split_whitespace().take(3).collect::<Vec<&str>>();
let ip = line_parts[0];
let bytes = line_parts[1];
let int_number = line_parts[2];

Is it possible to do something like this?

let [ip, bytes, int_number] = line.split_whitespace().take(3).collect();

I'm noticed various references to vector destructuring on some sites but the official docs don't seem to mention it.

Answer 1

It seems what you need is "slice patterns":

fn main() {
    let line = "127.0.0.1 1000 what!?";
    let v = line.split_whitespace().take(3).collect::<Vec<&str>>();

    if let [ip, port, msg] = &v[..] {
         println!("{}:{} says '{}'", ip, port, msg);
    }
}

Playground link

Note the if let instead of plain let. Slice patterns are refutable, so we need to take this into account (you may want to have an else branch, too).

Answer 2

You can also use this:

use std::convert::TryFrom;

let v = line.split_whitespace().take(3).collect::<Vec<&str>>();
let [ip, bytes, int_number] = <[&str; 3]>::try_from(v).ok().unwrap();

The return type of <[&str; 3]>::try_from(v) will be the Result type which you can use for error handling or allow it to panic as I did, since we already know that the size is 3.