Slices (&str / &[T])

// String slice
let s: &str = "hello";           // A string literal is of type &str.
let slice = &string[start..end]; // Gets a partial slice from a String.

// Array slice
let slice: &[i32] = &array[start..end];
let full: &[i32] = &array[..]; // A slice of the entire array.

fn first_word(s: &str) -> &str {
    let bytes = s.as_bytes();
    for (i, &item) in bytes.iter().enumerate() {
        if item == b' ' {
            return &s[0..i]; // Returns the portion before the first space.
        }
    }
    &s[..] // Returns the whole string if no space is found.
}

fn sum_slice(nums: &[i32]) -> i32 {
    nums.iter().sum()
}

fn main() {
    // String slice
    let s = String::from("hello world");
    let hello = &s[0..5];
    let world = &s[6..11];
    println!("{} {}", hello, world); // Prints "hello world".

    let word = first_word(&s);
    println!("First word: {}", word); // Prints "hello".

    // Array slice
    let a = [1, 2, 3, 4, 5];
    let slice = &a[1..4];
    println!("{:?}", slice); // Prints "[2, 3, 4]".

    println!("Sum: {}", sum_slice(&a)); // Prints "15".
}

Because a slice is a reference to the original data, no copying occurs. Using &str instead of String as a function parameter makes the function more flexible, since it accepts both string literals and String values.

Slicing a string that contains multi-byte characters (such as Japanese) at a non-character boundary will cause a runtime panic. To work with individual characters, use the chars() method (see String::chars()).

The lifetime of a slice is tied to its source data — once the source is freed, the slice becomes invalid. For more details, see Lifetimes ('a).