code1

use std::rc::Rc;
use std::rc::Weak;
use std::cell::RefCell;
use std::fmt;

struct Owner {
    name: String,
    gadgets: RefCell<Vec<Weak<Gadget>>>,//must be Weak instead Rc to avoid cyclic reference
}

trait Maker{
    fn make_gadget(&self, id: i32) -> Rc<Gadget>;
}

impl Maker for Rc<Owner> {
    fn make_gadget(&self, id: i32) -> Rc<Gadget> {
        let gadget = Rc::new(Gadget{id: id, owner: self.clone()});
        self.gadgets.borrow_mut().push(Rc::downgrade(&gadget));
        gadget
    }
}

impl fmt::Debug for Owner {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Owner {{ name: {}, gadgets: {:?} }}", self.name, self.gadgets.into_inner())
    }
}

#[derive(Debug)]
struct Gadget {
    id: i32,
    owner: Rc<Owner>,
}

fn main() {
    let gadget_owner : Rc<Owner> = Rc::new(
            Owner {
                name: "Gadget Man".to_string(),
                gadgets: RefCell::new(Vec::new()),
            }
        );

    let gadget1 = gadget_owner.make_gadget(1);
    let gadget2 = gadget_owner.make_gadget(2);
    println!("gadget1 is: {:?}", gadget1);
    println!("gadget2 is: {:?}", gadget2);
}