Function tao_of_rust::ch01::fly_dyn

pub fn fly_dyn(s: &dyn Fly) -> bool

零成本抽象 fly_dyn

struct Duck;
struct Pig;

trait Fly {
   fn fly(&self) -> bool;
}

impl Fly for Duck {
    fn fly(&self) -> bool {
        return true;
    }
}
impl Fly for Pig {
   fn fly(&self) -> bool {
       return false;
   }
}

fn fly_static<T: Fly>(s: T) -> bool {
   s.fly()
}

fn fly_dyn(s: &Fly) -> bool {
    s.fly()
}
assert_eq!(fly_dyn(&Pig), false);
assert_eq!(fly_dyn(&Duck), true);