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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

Practice 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.

Starter code

main.rs
fn main() {
    // buraya yaz
}

Sample solution

main.rs
struct Oyuncu {
    ad: String,
    puan: u32,
}

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

Expected output

Ece 120

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 How is a struct field accessed?

  • With brackets: o["puan"]
  • With an arrow: o->puan
  • With colons: o::puan
  • With a dot: o.puan Correct answer

Explanation: Rust always accesses fields with a dot; it auto-dereferences through references too.

2 Field type

Question 
struct Oyuncu {
    ad: String,
    puan: ____,
}
Answer 
struct Oyuncu {
    ad: String,
    puan: u32,
}

Explanation: The score is a non-negative integer; u32 is a suitable type.

3 Concept and example

Term Meaning
struct Oyuncu Type definition
ad: String Field
o.puan Field access
let mut o Mutable instance

All lessons in Beginner

1 Rust basics

  1. What is Rust?
  2. Project with Cargo
  3. Your first program
  4. println! and formatting
  5. Comments
  6. Summary - Rust basics

2 Variables

  1. Variables with let
  2. Mutability with mut
  3. Constants with const
  4. Static variables
  5. Shadowing
  6. Summary - Variables

3 Data types

  1. Integers
  2. Floating point
  3. Bool and char
  4. Tuple
  5. Array
  6. Summary - Data types

4 Strings

  1. &str vs String
  2. Creating a String
  3. Concatenating strings
  4. format! macro
  5. String length
  6. Summary - Strings

5 Project: Calculator

  1. Project skeleton
  2. Reading input
  3. Computing
  4. Error handling
  5. Loop and exit

6 Functions

  1. Defining with fn
  2. Parameters
  3. Return value
  4. Expressions and statements
  5. Early return
  6. Summary - Functions

7 Control flow

  1. if-else
  2. match basics
  3. loop
  4. while loop
  5. for loop
  6. Summary - Control flow

8 Ownership

  1. What is ownership?
  2. Move semantics
  3. Copy trait
  4. Functions and ownership
  5. Return and ownership
  6. Summary - Ownership

9 Borrowing

  1. References
  2. Mutable reference
  3. Borrowing rules
  4. Dangling reference
  5. References and functions
  6. Summary - Borrowing

10 Slices

  1. String slices
  2. Slice syntax
  3. Array slices
  4. Slices and functions
  5. Range types
  6. Summary - Slices

11 Project: Guessing game

  1. Game skeleton
  2. Reading input
  3. Comparing numbers
  4. Random number
  5. Loop and exit

12 Structs

  1. Struct definition
  2. Creating an instance
  3. Tuple struct
  4. Unit-like struct
  5. Field update
  6. Summary - Structs

13 Methods

  1. impl block
  2. self parameter
  3. &mut self
  4. Associated functions
  5. Multiple impl blocks
  6. Summary - Methods

14 Enums

  1. Enum definition
  2. Variants
  3. Variants with data
  4. Option<T>
  5. Option instead of null
  6. Summary - Enums

15 Pattern matching

  1. match patterns
  2. Value binding
  3. if let
  4. while let
  5. _ wildcard
  6. Summary - Pattern matching

16 Project: To-do CLI

  1. Task model
  2. Adding
  3. Listing
  4. Marking done
  5. Reading commands

17 Vectors

  1. Vec<T>
  2. Push and pop
  3. Index and get
  4. Looping a vector
  5. with_capacity
  6. Summary - Vectors

18 Advanced strings

  1. String and &str conversion
  2. chars and bytes
  3. Slicing strings
  4. contains and replace
  5. split and join
  6. Summary - Advanced strings

19 Error handling

  1. Result<T, E>
  2. panic!
  3. ? operator
  4. match and Result
  5. unwrap and expect
  6. Summary - Error handling

20 Beginner final

  1. Vowel counter
  2. Average calculator
  3. Bank account
  4. Temperature converter