rust - 一个for循环如何借用迭代器？

Question

for ... in 循环如何借用它正在运行的迭代器？例如:

let x = vec![1, 2, 3, 4];
let i = x.iter();
for a1 in i { break; } // iterate over just one "i"
for a2 in i { break; } // continue iterating through "i" here

你不能简单地将 &i 赋给 for，因为这样它就无法将 &Iterator 转换为 Iterator 对象。

Answer 1

您可以使用 Iterator::by_ref借用迭代器并在借用结束后继续使用它:

fn main() {
    let x = vec![1, 2, 3, 4];
    let mut i = x.iter();
    for _ in i.by_ref() { break; } // iterate over just one "i"
    for _ in i.by_ref() { break; } // continue iterating through "i" here
    assert_eq!(Some(&3), i.next())
}