main.rs

use downcast_rs::{impl_downcast, Downcast};

trait Command: Downcast {
    fn execute(&self);
}
impl_downcast!(Command);

#[derive(Debug, PartialEq)]
enum Temperature {
    Hot,
    Cold,
}

impl Command for Temperature {
    fn execute(&self) {
        println!("Temperature Command!");
    }
}

#[derive(Debug, PartialEq)]
enum Planet {
    Earth,
    Neptune,
}

impl Command for Planet {
    fn execute(&self) {
        println!("Planet Command!");
    }
}

fn main() {
    let a: Box<Command> = Box::new(Temperature::Hot);
    let also_a: Box<Command> = Box::new(Temperature::Hot);
    let not_a: Box<dyn Command> = Box::new(Temperature::Cold);

    let b = a.downcast_ref::<Temperature>();
    let also_b = also_a.downcast_ref::<Temperature>();
    let not_b = not_a.downcast_ref::<Temperature>();

    assert_eq!(b, also_b);
    assert_ne!(b, not_b);
}