Advanced Pattern Matching

Destructure Enum

Pull Fields from Variants

Pattern matching can unpack enum variants and bind the fields needed by each arm.

Program

Play the program to choose a command kind and watch the matching arm destructure it.

destructure_enum.rs 
fn main() {
    let kind = ;
    let command = make_command(kind);
    let text = describe(command);
    println!("{text}");
}

enum Command {
    Move { x: i32, y: i32 },
    Wait(i32),
    Quit,
}

fn make_command(kind: i32) -> Command {
    match kind {
        1 => Command::Move { x: 3, y: 4 },
        2 => Command::Wait(5),
        _ => Command::Quit,
    }
}

fn describe(command: Command) -> String {
    match command {
        Command::Move { x, y } => format!("move:{x},{y}"),
        Command::Wait(seconds) => format!("wait:{seconds}"),
        Command::Quit => "quit".to_string(),
    }
}

fn main() {
    let kind = ;
    let command = make_command(kind);
    let text = describe(command);
    println!("{text}");
}

enum Command {
    Move { x: i32, y: i32 },
    Wait(i32),
    Quit,
}

fn make_command(kind: i32) -> Command {
    match kind {
        1 => Command::Move { x: 3, y: 4 },
        2 => Command::Wait(5),
        _ => Command::Quit,
    }
}

fn describe(command: Command) -> String {
    match command {
        Command::Move { x, y } => format!("move:{x},{y}"),
        Command::Wait(seconds) => format!("wait:{seconds}"),
        Command::Quit => "quit".to_string(),
    }
}

fn main() {
    let kind = ;
    let command = make_command(kind);
    let text = describe(command);
    println!("{text}");
}

enum Command {
    Move { x: i32, y: i32 },
    Wait(i32),
    Quit,
}

fn make_command(kind: i32) -> Command {
    match kind {
        1 => Command::Move { x: 3, y: 4 },
        2 => Command::Wait(5),
        _ => Command::Quit,
    }
}

fn describe(command: Command) -> String {
    match command {
        Command::Move { x, y } => format!("move:{x},{y}"),
        Command::Wait(seconds) => format!("wait:{seconds}"),
        Command::Quit => "quit".to_string(),
    }
}
enum variant `Command::Move { x, y }` matches one variant and binds its fields.
tuple variant `Command::Wait(seconds)` binds the single value inside a tuple-like variant.
ownership `describe` takes ownership of the command and consumes it while matching.