Shared via Rust Playground

playground.rs

trait Entity {
    fn walk(&self) -> String;
}

struct Dog {
    name: String,
    age: i32
}

impl Dog {
    fn new(name: &str, age: i32) -> Dog {
        Dog{name: name.to_owned(), age: age}
    }
}

impl Entity for Dog {
    fn walk(&self) -> String {
        format!("{} who is {} years old, is walking.", self.name, self.age)
    }
}

impl Entity for Box<Entity> {
    fn walk(&self) -> String {
        self.walk()
    }
}

fn generate_entity() -> Box<Entity> {
    Box::new(Dog::new("marcel", 2))
}

fn process_entity<E: Entity>(ent: &E) -> &E {
    ent.walk();
    ent
}

fn main() {
    let p = generate_entity();
    let e = process_entity(&p);
    let f = e.clone();
    println!("{}", e.walk());
    println!("{}", p.walk());
    println!("{}", f.walk());
}