变体载荷

你可以定义更丰富的枚举，其中变体会携带数据。然后，你可以使用 match 语句从每个变体中提取数据：

enum WebEvent {
    PageLoad,                 // Variant without payload
    KeyPress(char),           // Tuple struct variant
    Click { x: i64, y: i64 }, // Full struct variant
}

#[rustfmt::skip]
fn inspect(event: WebEvent) {
    match event {
        WebEvent::PageLoad       => println!("page loaded"),
        WebEvent::KeyPress(c)    => println!("pressed '{c}'"),
        WebEvent::Click { x, y } => println!("clicked at x={x}, y={y}"),
    }
}

fn main() {
    let load = WebEvent::PageLoad;
    let press = WebEvent::KeyPress('x');
    let click = WebEvent::Click { x: 20, y: 80 };

    inspect(load);
    inspect(press);
    inspect(click);
}