مطابقة متغيرات enum

التعرّف على تعبير match

enum Light {
    Red,
    Green,
}

fn action(l: Light) {
    match l {
        Light::Red => println!("Stop"),
        Light::Green => println!("Go"),
    }
}

بنية ذراع match

match light {
    Light::Red => println!("Stop"),
    Light::Green => println!("Go"),
}

برنامج مطابقة كامل

enum TrafficLight {
    Red,
    Yellow,
    Green,
}

fn main() {
    let light = TrafficLight::Yellow;
    match light {
        TrafficLight::Red => println!("Stop"),
        TrafficLight::Yellow => println!("Slow down"),
        TrafficLight::Green => println!("Go"),
    }
}

يجب أن يكون match شاملًا

// This would FAIL to compile because
// the Green case is missing:
// match light {
//     Light::Red => println!("Stop"),
// }

النمط الشامل باستخدام _

enum Coin {
    Penny,
    Nickel,
    Dime,
    Quarter,
}

fn main() {
    let c = Coin::Dime;
    match c {
        Coin::Penny => println!("1 cent"),
        _ => println!("Some other coin"),
    }
}

يعيد match قيمة

enum Coin {
    Penny,
    Quarter,
}

fn main() {
    let coin = Coin::Quarter;
    let cents = match coin {
        Coin::Penny => 1,
        Coin::Quarter => 25,
    };
    println!("{} cents", cents);
}

أجسام الأذرع متعددة الأسطر

match light {
    Light::Red => {
        println!("Caution!");
        println!("Stop the car");
    }
    Light::Green => println!("Go"),
}

دمج الأنماط باستخدام |

enum Coin {
    Penny,
    Nickel,
    Dime,
    Quarter,
}

fn main() {
    let c = Coin::Nickel;
    match c {
        Coin::Penny | Coin::Nickel => println!("Small coin"),
        _ => println!("Bigger coin"),
    }
}

match في مقابل if/else

المطابقة والطباعة معًا

enum Direction {
    North,
    South,
    East,
    West,
}

fn main() {
    let d = Direction::West;
    let name = match d {
        Direction::North => "North",
        Direction::South => "South",
        Direction::East => "East",
        Direction::West => "West",
    };
    println!("Heading {}", name);
}

الترتيب مهم

تحقق سريع

مراجعة