Slices

A slice is a reference to a contiguous part of a collection. It lets you work with a portion of data without copying or owning it.

String slices

A string slice (&str) points to part of a String. Use a range inside brackets.

fn main() {
    let phrase = String::from("Hello, Rust");
    let hello = &phrase[0..5]; // characters 0 to 4
    let rust = &phrase[7..11]; // characters 7 to 10
    println!("{} {}", hello, rust);
}

You can omit the start or end of the range:

fn main() {
    let s = String::from("slices");
    let from_start = &s[..3]; // "sli"
    let to_end = &s[3..];     // "ces"
    let whole = &s[..];       // "slices"
    println!("{} {} {}", from_start, to_end, whole);
}

Array slices

Slices also work on arrays. The type of an integer slice is &[i32].

fn main() {
    let numbers = [10, 20, 30, 40, 50];
    let middle = &numbers[1..4]; // [20, 30, 40]
    println!("{:?}", middle);
    println!("{}", middle.len()); // 3
}

Because a slice borrows the original data, the collection must stay valid while the slice is in use. This is checked by the borrow rules.