参考Rust中的匹配值

Question

假设我有这个代码:

fn non_zero_rand() -> i32 {
    let x = rand();
    match x {
        0 => 1,
        _ => x,
    }
}

是否有简洁的方法将rand()匹配,然后将其绑定到一个值.像这样的事情:

fn non_zero_rand() -> i32 {
    match let x = rand() {
        0 => 1,
        _ => x,
    }
}

或者可能:

fn non_zero_rand() -> i32 {
    match rand() {
        0 => 1,
        _x => _x,
    }
}

Answer 1

一个简单的变量将匹配所有值并引入新变量,例如:

match rand() {
    0 => 1,
    x => x * 2,
}

创建变量并匹配它的更通用的方法是使用@模式:

match rand() {
    0 => 1,
    x @ _ => x * 2,
}

在这种情况下,没有必要,但在处理范围时它可能会很有用:

match code {
    None => Empty,
    Some(ascii @ 0 ... 127) => Ascii(ascii as u8),
    Some(latin1 @ 160 ... 255) => Latin1(latin1 as u8),
    _ => Invalid
}