| 14 | } |
| 15 | |
| 16 | fn main() { |
| 17 | let car: Rc<Car> = Rc::new( |
| 18 | Car { |
| 19 | name: "Tesla".to_string(), |
| 20 | wheels: RefCell::new(vec![]), |
| 21 | } |
| 22 | ); |
| 23 | let wl1 = Rc::new(Wheel { id:1, car: Rc::downgrade(&car) }); |
| 24 | let wl2 = Rc::new(Wheel { id:2, car: Rc::downgrade(&car) }); |
| 25 | |
| 26 | { |
| 27 | let mut wheels = car.wheels.borrow_mut(); |
| 28 | // downgrade 得到 Weak |
| 29 | wheels.push(Rc::downgrade(&wl1)); |
| 30 | wheels.push(Rc::downgrade(&wl2)); |
| 31 | } // 确保借用结束 |
| 32 | |
| 33 | for wheel_weak in car.wheels.borrow().iter() { |
| 34 | if let Some(wl) = wheel_weak.upgrade() { |
| 35 | println!("wheel {} owned by {}", wl.id, wl.car.upgrade().unwrap().name); |
| 36 | } else { |
| 37 | println!("wheel weak reference has been dropped"); |
| 38 | } |
| 39 | } |
| 40 | } |