What is the Rust equivalent to append in Go?

November 28, 2022

I am trying to figure out on my own reading through documentation, but with no luck on how to convert this Go function into Rust:

func main() {
  cards := []string{"Ace of Diamonds", newCard()}
  cards = append(cards, "Six of Spades")

  fmt.Println(cards)
}

func newCard() string {
  return "Five of Diamonds"
}

This is not correct, at least the cards.append I know is wrong:

fn main() {
    let mut cards: [&str; 2] = ["Ace of Diamonds", new_card()];
    let mut additional_card: [&str; 1] = ["Six of Spades"];
    cards.append(additional_card);

    println!("cards")
}

fn new_card() -> &'static str  {
    "Five of Diamonds"
}

>Solution :

You can’t. like in Go, Rust arrays are fixed size.

The type [&str; 2] in Rust is roughly equivalent to [2]string in Go, which you also can’t append to.

The closest to a Go slice you can get to in Rust is a Vec which you can use like this:

fn main() {
    let mut cards = vec!["Ace of Diamonds", new_card()];
    let additional_card: [&str; 1] = ["Six of Spades"];
    cards.extend(additional_card);
    // or for a single card
    cards.push("A single card");

    println!("{cards:?}")
}

fn new_card() -> &'static str  {
    "Five of Diamonds"
}