Structs and enums

struct Course {
    title: String,
    price: f64,
}

enum Level {
    Beginner,
    Intermediate,
    Advanced,
}

impl Course {
    fn describe(&self) -> String {
        format!("{} -- ${}", self.title, self.price)
    }
}

Rust's enums are more powerful than most languages' -- each variant can hold its own data, making them a natural fit for modeling things like API responses (success vs. error, each with different attached data).