将 &T 的迭代器收集到 T 集合中的惯用方法是什么? [英] What is an idiomatic way to collect an iterator of &T into a collection of Ts?

问题描述

我需要将 &strs 切片上的迭代器收集到 &strs 集合中.问题是迭代器产生 &&strs.

I need to collect an iterator over a slice of &strs into a collection of &strs. The problem is that the iterator yields &&strs.

我尝试从 &word 映射到 word，虽然它有效，但我不知道它是否被认为是好的，或者是否有更好的选择.

I tried to map from &word to word, and while it works, I don't know if it is considered good or if there are better options available.

问题:

use std::collections::HashSet;

fn main() {
    let words = &["hello", "world", "I'm", "a", "Rustacean!"];
    let hashset = words.iter().collect::<HashSet<&str>>();
}

游乐场p>

error[E0277]: a collection of type `std::collections::HashSet<&str>` cannot be built from an iterator over elements of type `&&str`
 --> src/main.rs:5:32
  |
5 |     let hashset = words.iter().collect::<HashSet<&str>>();
  |                                ^^^^^^^ a collection of type `std::collections::HashSet<&str>` cannot be built from `std::iter::Iterator<Item=&&str>`
  |
  = help: the trait `std::iter::FromIterator<&&str>` is not implemented for `std::collections::HashSet<&str>`

我的解决方案:

use std::collections::HashSet;

fn main() {
    let words = &["hello", "world", "I'm", "a", "Rustacean!"];
    let hashset = words.iter().map(|&w| w).collect::<HashSet<&str>>();
}

游乐场p>

推荐答案

如果 T 实现 Copy 那么你可以使用 Iterator::copied.否则，如果它实现 Clone 那么你可以使用 Iterator::cloned.像任何不可变引用一样，&str 实现了 Clone 和 Copy，因此您可以使用 copied:

If T implements Copy then you can use Iterator::copied. Otherwise, if it implements Clone then you can use Iterator::cloned. Like any immutable reference, &str implements both Clone and Copy, so you can use copied:

let hashset: HashSet<&str> = words.iter().copied().collect();

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