use std::collections::HashMap;

struct A {}
struct B {}

trait MyTrait {
    fn print_hello(&self);
}

impl MyTrait for A {
    fn print_hello(&self) {
        println!("I am A");
    }
}
impl MyTrait for B {
    fn print_hello(&self) {
        println!("I am B");
    }
}

fn main() {
    let a = Box::new(A {});
    let b = Box::new(B {});
    let mut dict: HashMap<&str, Box<dyn MyTrait>> = HashMap::new();
    dict.insert("a", a);
    dict.insert("b", b);

    match dict.get("a") {
        Some(my_trait) => {
            my_trait.print_hello();
        }
        None => {
            println!("Struct not found");
        }
    }
}