Trait Objects and Dynamic Dispatch

Trait Objects and Dynamic Dispatch

When heterogeneous collections are required at runtime, use dynamic dispatch via trait objects (dyn Trait):

trait Drawable {
    fn draw(&self);
}

struct Button;
impl Drawable for Button {
    fn draw(&self) { println!("Drawing button"); }
}

struct Checkbox;
impl Drawable for Checkbox {
    fn draw(&self) { println!("Drawing checkbox"); }
}

fn render_all(items: &[Box<dyn Drawable>]) {
    for item in items {
        item.draw();
    }
}

fn main() {
    let widgets: Vec<Box<dyn Drawable>> = vec![
        Box::new(Button),
        Box::new(Checkbox),
    ];
    render_all(&widgets);
}