Enums & Option Type

🦀 Rust Lesson 11 Intermediate

Enums in Rust are algebraic data types, allowing variants to hold associated data. Rust uses the Option enum to manage null safety explicitly.

1 Associated Data & Option Null Safety

Rust enums are incredibly versatile. Variants can hold different data types. Rust has **no null keyword**. Instead, null safety is handled explicitly using the built-in **`Option<T>`** enum:

`Some(value)`: The value exists.
`None`: No value exists (equivalent to null).

2 Enums Code

Let's run a program declaring enums with values and processing Option states:

Rust — Enums and Options ▶ Run Code

// Enum variants holding associated values
enum Message {
    Quit,
    Write(String),
}

fn main() {
    let msg = Message::Write(String::from("Hello variant"));

    match msg {
        Message::Quit => println!("Quit Variant"),
        Message::Write(text) => println!("Write Variant: {}", text),
    }

    // Option null safety check
    let score: Option = Some(95);
    let empty_score: Option = None;

    match score {
        Some(val) => println!("Score exists: {}", val),
        None => println!("No score found!"),
    }
}

3 Code Challenge

Challenge: Write a function that accepts an index and returns an `Option` from a list of user names. Use a match block to handle both success and error states.