FromIterator

FromIterator 让您可通过 Iterator 构建一个集合。

fn main() {
    let primes = vec![2, 3, 5, 7];
    let prime_squares = primes.into_iter().map(|p| p * p).collect::<Vec<_>>();
    println!("prime_squares: {prime_squares:?}");
}

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Iterator implements

fn collect<B>(self) -> B
where
    B: FromIterator<Self::Item>,
    Self: Sized

可以通过两种方式为此方法指定 B：

With the "turbofish": some_iterator.collect::<COLLECTION_TYPE>(), as shown. The _ shorthand used here lets Rust infer the type of the Vec elements.
使用类型推理功能时：let prime_squares: Vec<_> = some_iterator.collect()。将示例重写成使用这种形式。

There are basic implementations of FromIterator for Vec, HashMap, etc. There are also more specialized implementations which let you do cool things like convert an Iterator<Item = Result<V, E>> into a Result<Vec<V>, E>.

Comprehensive Rust 🦀

FromIterator