一、定义枚举

enum Message {
    Quit,
    Move {x:i32,y:i32},
    Write(String),
    ChangeColor(i32,i32,i32),
}

fn main() {
    let q = Message::Quit;
    let m = Message::Move{x:12,y:24};
    let w = Message::Write(String::from("Hello"));
    let c = Message::ChangeColor(0,255,255);
}