Namaran

shape_dyn.rs

trait Shape {
    fn area(&self) -> f64;

    fn describe(&self) -> String {
        format!("area = {:.1}", self.area())
    }

    fn scaled(&self, factor: f64) -> Self
    where
        Self: Sized;
}

struct Square {
    side: f64,
}

impl Shape for Square {
    fn area(&self) -> f64 {
        self.side * self.side
    }

    fn scaled(&self, factor: f64) -> Self {
        Square { side: self.side * factor }
    }
}

fn main() {
    let big = Square { side: 3.0 }.scaled(2.0);
    let shapes: Vec<Box<dyn Shape>> = vec![Box::new(big)];
    for s in &shapes {
        println!("{}", s.describe());
    }
}