rust循环引用问题

Posted 2022-11-29 吴冬冬

循环引用的时候需要使用weak，弱引用，一般把上级作为弱引用加到下级里

trait Sprite 
    fn draw(&self);
    fn update(&self);


struct Ball 
    game: RefCell<Weak<Game>>,


impl Sprite for Ball 
    fn draw(&self) 

    fn update(&self) 
        let g = self.game.borrow_mut().upgrade().expect("");
        let mut score = g.score.borrow_mut();
        *score = 1;
    


struct Paddle 
    game: RefCell<Weak<Game>>,


impl Sprite for Paddle 
    fn draw(&self) 

    fn update(&self) 

下级引用上级时普通的引用就OK了，要修改的就用RefCell，不用修改的就使用Rc

struct Game 
    score: RefCell<i32>,
    sprites: RefCell<Vec<Rc<Sprite>>>,


impl Game 
    fn draw(&mut self) 
        let ss = self.sprites.borrow_mut();

        for s in ss.iter() 
            s.draw();
        
    

下面是调用的方式

fn main() 
    let ball = Rc::new(
        Ball 
            game: RefCell::new(Weak::new())
        
    );

    let paddle = Rc::new(
        Paddle 
            game: RefCell::new(Weak::new())
        
    );

    let mut game = Rc::new(
        Game 
            score: RefCell::new(0),
            sprites: RefCell::new(vec![Rc::clone(&ball) as Rc<Sprite>, Rc::clone(&paddle) as Rc<Sprite>]),
        
    );

    *ball.game.borrow_mut() = Rc::downgrade(&game);
    *paddle.game.borrow_mut() = Rc::downgrade(&game);

    ball.update();

    println!("",game.score.borrow());