Struct definition

Define a fielded struct with struct.

Defining a struct

A struct is a custom type that groups related data under named fields. Each field has a name and a type:

struct Oyuncu {
    ad: String,
    puan: u32,
    aktif: bool,
}

Type names are written in PascalCase, field names in snake_case. The definition is only a template; memory is allocated when an instance is created.

Changing fields

To change a field, the whole instance must be mut; Rust doesn't allow marking individual fields as mutable:

let mut o = Oyuncu {
    ad: String::from("Ece"),
    puan: 120,
    aktif: true,
};
o.puan += 30;
println!("{} {}", o.ad, o.puan);   // Ece 150

Exercise First struct

Define an Oyuncu struct with the fields ad: String and puan: u32. Create an instance with ad = "Ece" and puan = 120, and print both fields separated by a space.

Show example solution

struct Oyuncu {
    ad: String,
    puan: u32,
}

fn main() {
    let o = Oyuncu {
        ad: String::from("Ece"),
        puan: 120,
    };
    println!("{} {}", o.ad, o.puan);
}

Test yourself

How is a struct field accessed?
- With brackets: o["puan"]
- With an arrow: o->puan
- With colons: o::puan
- With a dot: o.puan
Show answer

With a dot: o.puan — Rust always accesses fields with a dot; it auto-dereferences through references too.

Field type

struct Oyuncu {
    ad: String,
    puan: ____,
}

Show answer

struct Oyuncu {
    ad: String,
    puan: u32,
}

Concept and example

struct Oyuncu

Type definition
ad: String

Field
o.puan

Field access
let mut o

Mutable instance

Next lesson: Creating an instance

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