在 Rust 中只拆分一次字符串 [英] Split string only once in Rust

问题描述

我只想通过分隔符将字符串拆分一次并将其放入元组中.我试着做

I want to split a string by a separator only once and put it into a tuple. I tried doing

fn splitOnce(in_string: &str) -> (&str, &str) {
    let mut splitter = in_string.split(':');
    let first = splitter.next().unwrap();
    let second = splitter.fold("".to_string(), |a, b| a + b); 
    (first, &second)
}

但我一直被告知 second 的寿命不够长.我猜这是因为 splitter 只存在于功能块内，但我不确定如何解决这个问题.如何强制 second 超出功能块的存在?或者有没有更好的方法将字符串只拆分一次?

but I keep getting told that second does not live long enough. I guess it's saying that because splitter only exists inside the function block but I'm not really sure how to address that. How to I coerce second into existing beyond the function block? Or is there a better way to split a string only once?

推荐答案

您正在寻找 str::splitn:

You are looking for str::splitn:

fn split_once(in_string: &str) -> (&str, &str) {
    let mut splitter = in_string.splitn(2, ':');
    let first = splitter.next().unwrap();
    let second = splitter.next().unwrap();
    (first, second)
}

fn main() {
    let (a, b) = split_once("hello:world:earth");
    println!("{} --- {}", a, b)
}

注意 Rust 使用 snake_case.

Note that Rust uses snake_case.

我猜是因为splitter只存在于功能块内

I guess it's saying that because splitter only exists inside the function block

不，这是因为您创建了一个 String 并试图返回对它的引用；你不能这样做.second 是活得不够久.

Nope, it's because you've created a String and are trying to return a reference to it; you cannot do that. second is what doesn't live long enough.

如何将second强制转换为存在于功能块之外?

How to I coerce second into existing beyond the function block?

你没有.这是 Rust 的一个基本方面.如果某样东西需要存活一段时间，你只需要让它存在那么久.在这种情况下，就像在链接的问题中一样，您将返回 String:

You don't. This is a fundamental aspect of Rust. If something needs to live for a certain mount of time, you just have to make it exist for that long. In this case, as in the linked question, you'd return the String:

fn split_once(in_string: &str) -> (&str, String) {
    let mut splitter = in_string.split(':');
    let first = splitter.next().unwrap();
    let second = splitter.fold("".to_string(), |a, b| a + b); 
    (first, second)
}

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