在匹配块中获取匹配的表达式

Question

是否可以在匹配块中访问匹配的表达式？

考虑到这个例子，我应该用什么替换 HERE?

fn fetch_u32(args: &mut Vec<&str>) -> Result<u32,String> {
    match args.remove(0).parse::<u32>() {
        Ok(result) => Ok(result),
        Err(_) => Err("Argument '" + HERE + "' is not of type uint32".to_string())
    };
}

Answer 1

我会简单地提取之前的表达式，并在错误消息中重用绑定。

fn fetch_u32(args: &mut Vec<&str>) -> Result<u32, String> {
    let a = args.remove(0);
    match a.parse::<u32>() {
        Ok(result) => Ok(result),
        Err(_) => Err(format!("Argument '{}' is not of type uint32", a)),
    }
}

fn main() {
    let mut args = vec!["123", "bla", "456", "hop"];
    while !args.is_empty() {
        let r = fetch_u32(&mut args);
        println!("{:?}", r);
    }
}
/*
Ok(123)
Err("Argument 'bla' is not of type uint32")
Ok(456)
Err("Argument 'hop' is not of type uint32")
*/

在匹配块中获取匹配的表达式

Get matched expression inside match block

switch-statement

rust