如何从实现该特征的结构迭代器中收集特征向量

Question

I'm trying to get a vector of traits from an iterator of structs implementing that trait.

So far I was able to do this:

    fn foo() -> Vec<Box<dyn SomeTrait>> {
        let v: Vec<_> = vec![1]
            .iter()
            .map(|i| {
                let b: Box<dyn SomeTrait> = Box::new(TraitImpl { id: *i });
                b
            })
            .collect();
        v
    }

But I would like to make it more concise.

Answer 1

This works for me. Playground

Though I'm not a Rust guru, so I'm not sure about 'static limitation in foo<S: SomeTrait + 'static>

trait SomeTrait { fn echo(&self); }
impl SomeTrait for u32 {
    fn echo(&self) {
        println!("{}", self);
    }
}

fn foo<S: SomeTrait + 'static>(iter: impl Iterator<Item=S>) -> Vec<Box<dyn SomeTrait>> {
    iter.map(|e| Box::new(e) as Box<dyn SomeTrait>).collect()
}

fn main() {
    let v = vec!(1_u32, 2, 3);
    let sv = foo(v.into_iter());
    sv.iter().for_each(|e| e.echo());
}