Match, if let, While let

enum Coin {
    Penny,
    Nickel,
    Dime,
    Quarter(String),
}

fn value_in_cents(coin: Coin) -> u8 {
    match coin {
        Coin::Penny => 1,
        Coin::Nickel => 5,
        Coin::Dime => 10,
        Coin::Quarter(state) => {
            // pattern binding to value
            println!("State quarter from {:?}!", state);
            25
        } // if needed, use catchall _ =>
    }
}

fn main() {
    println!("{}", value_in_cents(Coin::Penny));
}

// struct pattern matching
struct Point {
    x: i32,
    y: i32,
    z: i32,
}

fn main() {
    let origin = Point { x: 0, y: 0, z: 0 };

    match origin {
        // Ignoring all fields of a Point except for x by using ..
        Point { x, .. } => println!("x is {}", x),
    }
}

Patterns accept 1 | 2 for or, 1..=5 for inclusive range, if x % 2 == 0 guards, @-binding Message::Hello { id: id_variable @ 3..=7,}.

if let

if let

fn main() {
    let config_max = Some(3u8);
    if let Some(max) = config_max {
        // <-- if let
        println!("The maximum is configured to be {}", max);
    }
}

while let

while let

    let mut stack = Vec::new();

    stack.push(1);
    stack.push(2);
    stack.push(3);

    while let Some(top) = stack.pop() {
        // <-- while let
        println!("{}", top);
    }

See Also

• Control Flow.
• Error Handling.
• Option.
• Result.
• Rust Patterns.

References

• Pattern matching⮳.