factory_rust.rs

pub trait Command {
    fn execute(&self) -> String;
}

struct AddCmd;
struct DeleteCmd;

impl Command for AddCmd {
    fn execute(&self) -> String { "It add".into() } 
}

impl Command for DeleteCmd { 
    fn execute(&self) -> String { "It delete".into() }
}

fn command(s: &str) -> Option<Box<Command+'static>> {
    match s {
        "add" => Some(Box::new(AddCmd)),
        "delete" => Some(Box::new(DeleteCmd)),
        _ => None
    }
}

fn main() {
    let a = command("add").unwrap();
    let d = command("delete").unwrap();
    println!("{}", a.execute());
    println!("{}", d.execute());
}