Dynamic dispatch with Box and trait objects. Function handler.

dynamic_dispatch.rs

trait Handler {
    fn handle(&self);
}

struct Data1 {
    v: i32,
}
impl Handler for Data1 {
    fn handle(&self) {
        println!("Data1: {}", self.v);
    }
}

struct Data2;
impl Handler for Data2 {
    fn handle(&self) {
        println!("Data2");
    }
}

struct Func<F: Fn()> {
    f: F,
}
impl<F: Fn()> Func<F> {
    fn new(f: F) -> Func<F> {
        Func {
            f,
        }
    }
}
impl<F: Fn()> Handler for Func<F> {
    fn handle(&self) {
        (self.f)()
    }
}

fn proc(handlers: Vec<&dyn Handler>) {
    for h in handlers {
        h.handle();
    }
}

fn make(i: i32) -> Box<dyn Handler> {
    if i < 10 {
        Box::new(Data1{v: 32})
    } else if i < 15 {
        Box::new(Func::new(|| println!("Func")))
    }
    else {
        Box::new(Data2)
    }
}

fn main()  {
    let d1 = make(5);
    let d2 = make(15);
    let f = make(12);
    
    proc(vec![&*d1, &*d2, &*f]);
}