rust - 查看 `for` 循环内的迭代器

Question

我试图在遍历 &str 时查看当前位置前面的字符。

let myStr = "12345";
let mut iter = myStr.chars().peekable();
for c in iter {
    let current: char = c;
    let next: char = *iter.peek().unwrap_or(&'∅');
}

我会将这个字符传递到一个方法中。然而，即使是这个 MRE 也会产生移动错误后的借用，我不确定如何克服。

error[E0382]: borrow of moved value: `iter`
   --> src/lib.rs:7:27
    |
4   |     let mut iter = myStr.chars().peekable();
    |         -------- move occurs because `iter` has type `Peekable<Chars<'_>>`, which does not implement the `Copy` trait
5   |     for c in iter {
    |              ---- `iter` moved due to this implicit call to `.into_iter()`
6   |         let current: char = c;
7   |         let next: char = *iter.peek().unwrap_or(&'∅');
    |                           ^^^^^^^^^^^ value borrowed here after move
    |
note: this function takes ownership of the receiver `self`, which moves `iter`
   --> /home/james/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/iter/traits/collect.rs:267:18
    |
267 |     fn into_iter(self) -> Self::IntoIter;

知道这里发生了什么吗？我尝试了引用和取消引用的各种组合，但我尝试过的似乎都不起作用。

Answer 1

迭代器被移动到 for 循环中。您不能在 for 循环内手动操作迭代器。但是，for 循环可以替换为 while let:

while let Some(c) = iter.next() {
    let current: char = c;
    let next: char = *iter.peek().unwrap_or(&'∅');
}

Playground .