Rust - show how to return a trait

main.rs

trait Handle {
    fn handle(&self) -> String;
}

struct Command<T> {
    pub payload: T
}

struct Jump {
    pub how_high: i32
}

struct Marco {
    pub polo: String
}

impl Handle for Command<Jump> {
    fn handle(&self) -> String {
        format!("Jumping {}", self.payload.how_high)
    }
}

impl Handle for Command<Marco> {
    fn handle(&self) -> String {
        format!("Polo: {:?}", self.payload.polo)
    }
}

const JUMP: &str = "jump";
const MARCO: &str = "marco";

// Notice the Box<dyn X>
fn get_handler(cmd: &str) -> Option<Box<dyn Handle>> {
    match cmd {
        JUMP => Some(Box::new(Command { payload: Jump { how_high: 10 }})),
        MARCO => Some(Box::new( Command { payload: Marco { polo: "polo".to_string() }})),
        _ => None
    }
}

fn main() {
    assert_eq!(get_handler("jump").unwrap().handle(), "Jumping 10".to_string());
    assert_eq!(get_handler("marco").unwrap().handle(), "Polo: \"polo\"".to_string());
    assert_eq!(get_handler("Nothing").is_none(), true);
}