【Rust】trait实现

环境

• Rust 1.56.1
• VSCode 1.61.2

概念

参考：https://doc.rust-lang.org/rust-by-example/trait/impl_trait.html

示例

静态返回

fn combine_vecs(v: Vec<i32>, u: Vec<i32>) -> impl Iterator<Item = i32> {
    v.into_iter().chain(u.into_iter()).cycle()
}

fn main() {
    let v1 = vec![1, 2, 3];
    let v2 = vec![4, 5];
    let mut v3 = combine_vecs(v1, v2);
    assert_eq!(Some(1), v3.next());
    assert_eq!(Some(2), v3.next());
    assert_eq!(Some(3), v3.next());
    assert_eq!(Some(4), v3.next());
    assert_eq!(Some(5), v3.next());
    println!("all done");
}

返回闭包

fn make_adder_function(y: i32) -> impl Fn(i32) -> i32 {
    move |x| x + y
}

fn main() {
    let plus_one = make_adder_function(1);
    assert_eq!(plus_one(2), 3);
}

返回迭代器

fn double_positives<'a>(numbers: &'a Vec<i32>) -> impl Iterator<Item = i32> + 'a {
    numbers.iter().filter(|x| x > &&0).map(|x| x * 2)
}

fn main() {
    double_positives(&vec![1, 2]).count();
}

总结

了解了 Rust 中 impl trait 的使用方法。

附录