rust 基础03

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枚举

定义

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enum Message {
    Quit, // 常量标识
    Move{x:i32,y:i32}, // 匿名结构体
    Write(String), // 字符串
    ChangeColor(i32,i32,i32) // 元组或数组数据
}

定义方法

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enum Message {
    Quit, // 常量标识
    Move{x:i32,y:i32}, // 匿名结构体
    Write(String), // 字符串
    ChangeColor(i32,i32,i32) // 元组或数组数据
}

impl Message{
    fn call(&self){}
}

fn main() {
    let q = Message::Quit;
    let m = Message::Move { x: 20, y: 30 };
    let w = Message::Write(String::from("hello"));
    let c = Message::ChangeColor(200, 300, 400);

    m.call();
}

Option枚举

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// Option的定义
enum Option<T> {
    None,
    Some(T),
}
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// Option枚举用例
let some_number = Some(5);
let some_string = Some("a string");
 
let absent_number: Option<i32> = None;

Match 匹配

举例

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enum Week {
    Monday,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday,
    Sunday
}

fn main() {
    let num =  week_num(Week::Friday);
    println!("{}",num)  
}

fn week_num(w:Week) -> u8{
    match w {
        Week::Monday => 1,
        Week::Tuesday => 2,
        Week::Wednesday => 3,
        Week::Thursday => 4,
        Week::Friday => 5,
        Week::Saturday => 6,
        Week::Sunday => 7,
    }
}
  • 注意：match匹配的值必须进行穷举，如果没必要都匹配的话使用 _ 匹配剩余的值
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    fn week_num(w:Week) -> u8{
        match w {
            Week::Monday => 1,
            Week::Tuesday => 2,
            Week::Wednesday => 3,
            _ => 0
        }
    }

使用 mat处理option枚举数据

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fn main() {
    let five = Some(5);
    let _six = plus_one(five);
    let _none = plus_one(None);
}

fn plus_one(x:Option<i32>)-> Option<i32> {
    match x {
        None => {
            println!("是个空值");
            None
        },
        Some(i) => {
            println!("{}",i);
            Some(i+1)
        }
    }
}