Strings

Owned String vs &str

&str is a view into text. String owns growable UTF-8 data.

let slice: &str = "hello";
let owned: String = String::from("hello");
println!("{slice} {owned}");

Append and format

Push text onto a String or build with format!.

let mut s = String::from("hi");
s.push_str(" there");
let msg = format!("{s}!");
println!("{msg}");

Pass string slices to functions

Prefer &str parameters so both String and literals work.

fn shout(text: &str) {
    println!("{}", text.to_uppercase());
}

shout("rust");
shout(&owned);

UTF-8 caution

• Indexing by byte can panic on multibyte characters
• Iterate with .chars() when you need Unicode scalars
• Length in bytes and length in chars can differ
• Use the standard library docs when slicing text