Tuple struct

Learn the tuple struct type and when to use it.

Tuple structs

When field names are unnecessary, a tuple struct is used; fields are accessed with .0 and .1:

struct Renk(u8, u8, u8);
struct Nokta3(i32, i32, i32);

let turuncu = Renk(255, 128, 0);
println!("{}", turuncu.0);   // 255

Even though Renk and Nokta3 have the same shape, they are different types; one can't be passed where the other is expected.

Newtype and destructuring

A single-field tuple struct is called a newtype. Its value can be unpacked with a pattern:

struct Metre(f64);
struct Saniye(f64);

fn hiz(m: Metre, s: Saniye) -> f64 {
    let Metre(yol) = m;
    yol / s.0
}

println!("{}", hiz(Metre(100.0), Saniye(8.0)));   // 12.5

Writing hiz(Saniye(8.0), Metre(100.0)) is a compile error; the mix-up in order is caught.

Exercise Colour code

Define struct Renk(u8, u8, u8); and create Renk(255, 128, 0). Print the fields side by side with the {:02X} format to produce #FF8000.

Show example solution

struct Renk(u8, u8, u8);

fn main() {
    let k = Renk(255, 128, 0);
    println!("#{:02X}{:02X}{:02X}", k.0, k.1, k.2);
}

Test yourself

What is the "newtype" pattern for?
- Provides inheritance
- Separates meaning over the same base type: Metre(f64) and Saniye(f64) can't be mixed up
- Speeds up the program
- Allocates memory
Show answer

Separates meaning over the same base type: Metre(f64) and Saniye(f64) can't be mixed up — A single-field tuple struct adds type safety with no runtime cost.

Field access

struct Renk(u8, u8, u8);
let k = Renk(10, 20, 30);
let yesil = k.____;   // 20

Show answer

struct Renk(u8, u8, u8);
let k = Renk(10, 20, 30);
let yesil = k.1;   // 20

Definition and kind

struct Renk(u8, u8, u8);

Tuple struct
struct Metre(f64);

Newtype
struct Oyuncu { ad: String }

Named-field struct
let Metre(yol) = m;

Unpacking with a pattern

Next lesson: Unit-like struct

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