use std::{cell::RefCell, rc::Rc};

#[derive(Default)]
struct Loopy {
    thing: RefCell<Option<Box<Fn()>>>,
}

impl Loopy {
    fn tie_the_knot(self: Rc<Self>) {
        let me = self.clone();
        *self.thing.borrow_mut() = Some(Box::new(move || {
            println!("Is set? {}", me.thing.borrow().is_some());
        }))
    }
}

fn main() {
    let l = Rc::new(Loopy::default());
    l.clone().tie_the_knot();

    let f = l.thing.borrow();
    if let Some(f) = &*f {
        f();
    }
}