如何从实现 Trait 的类型向量创建新的 Trait 向量? [英] How do I create a new vector of Trait from vectors of types that implement Trait?

问题描述

我想创建一个包含实现 Trait 的对象的新向量，从我已经拥有的一些包含这些对象的向量中.

I would like to create a new vector that contains objects that implement Trait, from some vectors I already have which contain those objects.

trait Foo {
    //
}


struct Bar {
    i: i32,
}


struct Baz {
    c: char,
}

impl Foo for Bar {
    //
}

impl Foo for Baz {
    //
}
fn main() {
    let v1 = vec![Bar{i: 2},Bar{i: 4}];
    let v2 = vec![Baz{c: '2'},Baz{c: '4'}];

    let mut v_all: Vec<Box<Foo>> = Vec::new();

    v_all.extend(v1.into_iter());
    v_all.extend(v2.into_iter());

}

这当然让我着迷

<anon>:34:11: 34:33 error: type mismatch resolving `<collections::vec::IntoIter<Bar> as core::iter::Iterator>::Item == Box<Foo>`: expected struct Bar, found box
<anon>:34     v_all.extend(v1.into_iter());

如果可能，我怎样才能做到这一点?

How could I achieve this, if possible?

推荐答案

好吧，如果你有一个 Bar，并且你需要一个 Box，那么你需要先将值装箱，然后将其转换为 trait 对象，如下所示:

Well, if you have a Bar, and you need a Box<Foo>, then you need to first box the value, then cast it to a trait object, which looks like this:

v_all.extend(v1.into_iter().map(|e| Box::new(e) as Box<Foo>));
v_all.extend(v2.into_iter().map(|e| Box::new(e) as Box<Foo>));

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