trait_object.rs

trait Animal {
    fn speak(&self);
}

struct Dog;

impl Animal for Dog {
    fn speak(&self) {
        println!("Woof");
    }
}

impl Dog {
    pub fn new() -> Dog {
        Dog {

        }
    }
}

struct Cat;

impl Cat {
    pub fn new() -> Cat {
        Cat {

        }
    }
}

impl Animal for Cat {
    fn speak(&self) {
        println!("Meow");
    }
}

struct Zoo {
    pub animals: Vec<Box<Animal>>,
}

impl Zoo {
    pub fn new() -> Zoo {
        Zoo {
            animals: vec![],
        }
    }

    pub fn add_cat(&mut self) {
        self.animals.push(Box::new(Cat::new()));
    }

    pub fn add_dog(&mut self) {
        self.animals.push(Box::new(Dog::new()));
    }
}

fn main() {

    let mut zoo = Zoo::new();
    zoo.add_cat();
    zoo.add_cat();
    zoo.add_dog();
    zoo.add_cat();
    zoo.add_dog();

    for animal in zoo.animals {
        animal.speak();
    }

}