Lifetimes and References

String Slice

Borrowing Part of Text

A string slice borrows a range of bytes from existing text. The borrowed slice cannot outlive the original string.

Program

Play the program to choose how much of a word is borrowed as a slice.

take
string_slice.rs
Replay: real traced execution (multi-file project)
fn main() {
    let text = "rustacean";
    let take = 4;
    let part = &text[..take];
    println!("{part}");
}

fn main() {
    let text = "rustacean";
    let take = 5;
    let part = &text[..take];
    println!("{part}");
}

fn main() {
    let text = "rustacean";
    let take = 9;
    let part = &text[..take];
    println!("{part}");
}

  1. text ← "rustacean", take ← 4, part ← "rust"

    1fn main() {2    let tex→ "rustacean"t = "rustacean";3    let tak→ 4e = 4; //@take=5, 94    let par→ "rust"t = &text[..take"rust"];5    println!("{part}");6}
    outputrust

  1. text ← "rustacean", take ← 5, part ← "rusta"

    1fn main() {2    let tex→ "rustacean"t = "rustacean";3    let tak→ 5e = 5;4    let par→ "rusta"t = &text[..take"rusta"];5    println!("{part}");6}
    outputrusta

  1. text ← "rustacean", take ← 9, part ← "rustacean"

    1fn main() {2    let tex→ "rustacean"t = "rustacean";3    let tak→ 9e = 9;4    let par→ "rustacean"t = &text[..take"rustacean"];5    println!("{part}");6}
    outputrustacean
string slice `&text[..take]` borrows part of the string data.
borrowed view The slice points into `text`; it does not allocate a new string.
valid boundary Slice indexes must land on UTF-8 character boundaries.