Rust 转换readline'；将ReadlineBytes转换为字符串

我正在尝试创建一个带有readline命令提示符的程序

我用的是板条箱

这是存储库中的示例。（板条箱页面上有存储库链接。）

我正在尝试将

s

从

readline:：common:：ReadlineBytes

转换为

std:：string:：string

，这样我就可以像这样对它进行

匹配

while let Ok(s) = readline(&prompt){
    let command = str::from_utf8(&s.to_bytes()).unwrap();
    match command {
        "exit"  => std::process::exit,
        "again" => break,
        _ => println!("error")
    }
    println!("{}", command);
}

但我一直在犯这样的错误：

main.rs:18:9: 22:10 error: match arms have incompatible types:
 expected `fn(i32) -> ! {std::process::exit}`,
    found `()`
(expected fn item,
    found ()) [E0308]
main.rs:18         match command {
main.rs:19             "exit"  => std::process::exit,
main.rs:20             "again" => break,
main.rs:21             _ => println!("error")
main.rs:22         }
note: in expansion of while let expansion
main.rs:16:5: 24:6 note: expansion site
main.rs:18:9: 22:10 help: run `rustc --explain E0308` to see a detailed explanation
main.rs:21:18: 21:35 note: match arm with an incompatible type
main.rs:21             _ => println!("error")
                            ^~~~~~~~~~~~~~~~~
note: in expansion of while let expansion
main.rs:16:5: 24:6 note: expansion site
error: aborting due to previous error

匹配臂都必须返回相同的类型。再次查看您的错误消息：

main.rs:18:9: 22:10 error: match arms have incompatible types:
 expected `fn(i32) -> ! {std::process::exit}`,
    found `()`
(expected fn item,
    found ()) [E0308]

您的一个匹配臂正在返回
（）
，另一个正在返回类型
fn（i32）->！{std:：process:：exit}
-一个函数

看看你的代码：

"exit"  => std::process::exit,

您没有调用
exit
，您只是返回对它的引用。
我们中的一些人已经编写了readline包装程序。我的更容易用在普通情况下。@SeanPerry，你是说？这看起来简单多了。谢谢
main.rs:18:9: 22:10 error: match arms have incompatible types:
 expected `fn(i32) -> ! {std::process::exit}`,
    found `()`
(expected fn item,
    found ()) [E0308]

"exit"  => std::process::exit,