rust中的match表达式使用详解

fn main() {
    println!("penny {}", value_in_cents(Coin::Penny)) // penny 1
}
enum Coin {
    Penny,
    Nickel,
    Dime,
    Quarter,
}
fn value_in_cents(coin: Coin) -> u8 {
    match coin {
        Coin::Penny => 1,
        Coin::Nickel => 5,
        Coin::Dime => 10,
        Coin::Quarter => {
            println!("多行的情况需要加上花括号");
            25
        },
    }
}

fn main() {
    println!("penny {}", value_in_cents(Coin::Quarter(UsState::Alabama))) // State quarter from Alabama\n penny 25 
}
#[derive(Debug)]
enum UsState {
    Alabama,
    Alaska,
}
enum Coin {
    Penny,
    Nickel,
    Dime,
    Quarter(UsState),
}
fn value_in_cents(coin: Coin) -> u8 {
    match coin {
        Coin::Penny => 1,
        Coin::Nickel => 5,
        Coin::Dime => 10,
        // 绑定值的模式匹配
        Coin::Quarter(state) => {
            println!("State quarter from {:?}", state);
            25
        },
    }
}

fn main() {
    let v = 0u8;
    match v {
        1 => println!("one"),
        2 => println!("two"),
        3 => println!("three"),
        // 其他的不想匹配了，可以使用`_`替代，下换线通配符只能放到最后一行
        _ => println!("other")
    }
}

fn main() {
    let v = 0u8;
    match v {
        1 => println!("one"),
        2 => println!("two"),
        3 => println!("three"),
        // 其他的不想匹配了，可以使用`_`替代，下换线通配符只能放到最后一行
        _ => println!("other"),
    }
    // 可以使用let进行简写
    if let 3 = v {
        println!("three");
    } else {
        println!("other")
    }
}

fn main() {
    let five = Some(5);
    let six = plus_one(five);
    let none = plus_one(None);
    // 使用模式匹配和Option可以避免其他语言出现NPE的问题
    match six {
        Some(value) => println!("six: {}", value),
        None => println!("six: None"),
    }
    match none {
        Some(value) => println!("none: {}", value),
        None => println!("none: None"),
    }
}
fn plus_one(x: Option<i32>) -> Option<i32> {
    match x {
        None => None,
        Some(i) => Some(i + 1)
    }
}