Deriving Debug in Rust Lets Us Inspect a Struct

A new struct does not automatically have a display format. If we want to inspect its fields while developing, we can derive Debug and print it with the {:?} formatter in source

#[derive(Debug)]
struct Movie {
    title: String,
    year: u16,
}
 
fn main() {
    let movie = Movie {
        title: String::from("Arrival"),
        year: 2016,
    };
 
    println!("{movie:?}");
}

If you’ll run this, you’ll get Movie { title: "Arrival", year: 2016 }

Remove #[derive(Debug)] and run cargo check. Rust tells us that Movie does not implement Debug. The derive attribute asks Rust to generate that implementation. Debug is useful for inspecting values during development; a polished format for readers is a separate choice.