Rust控制流运算符match的用法详解

match value {
    pattern1 => {
        //code1
    }
    pattern2 => {
        //code2
    }
    _ => {
        //没有任何匹配
    }
}

//一个枚举和一个以枚举成员作为模式的match表达式
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 => 25,
    }
}

fn value_in_cents(coin:Coin) -> u8 {
    match coin {
        Coin::Penny => {
            println!("Lucy penny!");
            1
        }
        Coin::Nickel => 5,
        Coin::Dime => 10,
        Coin::Quarter =>25,
    }
}

//Quarter成员也存放一个UsState值的Coin枚举
#[derive(Debug)]
enum UsState {
    Alabama,
    Alaska,
    //--snip--
}
 
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,
        Coin::Quarter(state) => {
            println!("State quarter from {:?}!", state);
            25
        }
    }
}

// 一个Option<i32>上使用match表达式的函数
fn plus_one (x: Option<i32>) -> Option<i32> {
    match x {
        None => None,
        Some(i) => Some(i+1),
    }
}
 
let five = Some(5);
let six =plus_one(five);
let none = plus_one(None);

let dice_roll = 9;
match dice_roll {
    3 => add_fancy_hat(),
    7 => remove_fancy_hat(),
    other => move_player(other),
}
 
fn add_fancy_hat() {}
fn remove_fancy_hat() {}
fn move_player(num_spaces: u8) {}

let dice_roll = 9;
match dice_roll {
    3 => add_fancy_hat(),
    7 => remove_fancy_hat(),
    _ => reroll(),
}
 
fn add_fancy_hat() {}
fn remove_fancy_hat() {}
fn reroll() {}

let dice_roll = 9；
match dice_roll {
    3 => add_fancy_hat(),
    7 => remove_fancy_hat(),
    _ => (),
}
 
fn add_fancy_hat() {}
fn remove_fancy_hat() {}