fn string_slice(arg: &str) { println!("{arg}"); } fn string(arg: String) { println!("{arg}"); } fn main() { string_slice("blue"); string("red".to_string()); string(String::from("hi")); string("rust is fun!".to_owned()); // Here, both answers work. // `.into()` converts a type into an expected type. // If it is called where `String` is expected, it will convert `&str` to `String`. string("nice weather".into()); // But if it is called where `&str` is expected, then `&str` is kept `&str` since no conversion is needed. // If you remove the `#[allow(…)]` line, then Clippy will tell you to remove `.into()` below since it is a useless conversion. #[allow(clippy::useless_conversion)] string_slice("nice weather".into()); string(format!("Interpolation {}", "Station")); // WARNING: This is byte indexing, not character indexing. // Character indexing can be done using `s.chars().nth(INDEX)`. string_slice(&String::from("abc")[0..1]); string_slice(" hello there ".trim()); string("Happy Monday!".replace("Mon", "Tues")); string("mY sHiFt KeY iS sTiCkY".to_lowercase()); }