use std::collections::HashMap;

trait Trait {
    fn metodo(&self) -> usize {
        0
    }

    fn altro_metodo() -> usize;
}

struct Foo;

impl Trait for Foo {
    fn altro_metodo() -> usize {
        1
    }
}

fn main() -> Result<(), String> {
    let mut dictionary: HashMap<String, Box<Trait>> = HashMap::new();
    dictionary.insert(String::from("bar"), Box::new(Foo));

    dictionary.get("bar")
                .ok_or_else(|| String::from("\"bar\" not found"))
                .and_then(|o| {
                    println!("{}", o.metodo());
                    Ok(())
                })
}