Rust Tutorial · Structs, Enums and Collections · Lesson 15 of 29

Rust Pattern Matching

Use match, if let, let else and let chains to destructure values and handle cases exhaustively.

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match

match must cover every possible value (the compiler checks), and patterns can include ranges, multiple values and guards (if conditions).

match with ranges and guards

fn classify(status: u16) -> &'static str {
    match status {
        200 | 201 | 204 => "success",
        300..=399 => "redirect",
        404 => "not found",
        code if code >= 500 => "server error",
        _ => "client error",
    }
}

fn main() {
    for code in [200, 301, 404, 418, 503] {
        println!("{code}: {}", classify(code));
    }
}

Output

200: success
301: redirect
404: not found
418: client error
503: server error

Run this on your computer — see “Get Started” for setup.

if let, let else and let chains

if let Some(x) = value { ... } handles one pattern.
let Some(x) = value else { return ... }; unwraps or exits early.
Let chains (Rust 2024 edition) combine patterns and conditions: if let Some(u) = user && u.active { ... }.

let else and let chains

struct User { name: String, active: bool }

fn greeting(user: Option<&User>) -> String {
    let Some(user) = user else {
        return "Hello, guest".to_string();
    };
    format!("Hello, {}", user.name)
}

fn main() {
    let ana = User { name: "Ana".into(), active: true };
    println!("{}", greeting(Some(&ana)));
    println!("{}", greeting(None));
    let maybe_user = Some(&ana);
    if let Some(u) = maybe_user && u.active {
        println!("{} is active", u.name);
    }
}

Output

Hello, Ana
Hello, guest
Ana is active

Run this on your computer — see “Get Started” for setup.

Test yourself

What happens if a match doesn't cover every case?

It panics at runtime
The program doesn't compile
Nothing happens for missing cases
A warning is printed

Show answer

Answer: The program doesn't compile

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