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Structs, Enums and Traits

Rust Structs

Group related values into your own type with named fields.

  • Intermediate
  • 3 min read
  • 1 runnable example
What you'll learn
  • Defining a struct
  • Reading and changing fields
  • Struct update syntax
Run code →
User
name"Ada"
age37
activetrue

Your own type with named fields

A struct is a type you define by naming its fields. It keeps related data together, such as the name, age and status of a user.

A struct value must be declared mut before a field can change. #[derive(Debug)] lets {:?} print the whole struct. ..user fills the fields that are not listed from another value, here only age.

Key points

  1. A struct value must be mut to change a field.
  2. #[derive(Debug)] lets {:?} print it.
  3. ..user copies the remaining fields.

Runnable Rust example

Rust
Run code →
main.rs
#[derive(Debug)]
struct User {
    name: String,
    age: u32,
    active: bool,
}

fn main() {
    let mut user = User {
        name: String::from("Ada"),
        age: 36,
        active: true,
    };
    user.age += 1;

    println!("{} is {}", user.name, user.age);
    println!("{:?}", user);

    let guest = User { name: String::from("Guest"), active: false, ..user };
    println!("{} {} {}", guest.name, guest.age, guest.active);
}
Get a Run button for this example Result of running the code
Ada is 37
User { name: "Ada", age: 37, active: true }
Guest 37 false

Practice

Open the example in the online compiler, change a value or add a line, and predict the output before you run it. Then break the code on purpose and read the compiler's message.

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