1. In the bin folder, create a file called shared.rs

2. Add the following code and run it with cargo run --bin shared:

1    use std::rc::Rc;
2 
3    // The ball will survive until all kids are done playing with 
        it
4    struct Kid {
5      ball: Rc<Ball>,
6    }
7    struct Ball;
8 
9    fn main() {
10     {
11       // rc is created and count is at 1
12       let foo = Rc::new("foo");
13       // foo goes out of scope; count decreases
14       // count is zero; the object gets destroyed
15     }
16 
17     {
18       // rc is created and count is at 1
19       let bar = Rc::new("bar");
20       // rc is cloned; count increases to 2
21       let second_bar = Rc::clone(&bar);
22       // bar goes out of scode; count decreases to 1
23       // bar goes out of scode; count decreases to 0
24     }
25 
26     {
27       // rc is created and count is at 1
28       let baz = Rc::new("baz");
29       {
30         // rc is cloned; count increases to 2
31         let second_baz = Rc::clone(&baz);
32         // second_baz goes out of scode; count decreases to 1
33       }
34       // baz goes out of scode; count decreases to 0
35     }
36     let kid_one = spawn_kid_with_new_ball();
37     let kid_two = Kid {
38       ball: Rc::clone(&kid_one.ball),
39     };
40     let kid_three = Kid {
41       ball: Rc::clone(&kid_one.ball),
42     };
43     // ball lives until here
44   }
45 
46   fn spawn_kid_with_new_ball() -> Kid {
47     let ball = Rc::new(Ball);
48     Kid {
49       ball: Rc::clone(&ball),
50     }
51     // Although the ball goes out of scope here, the object 
          behind it
52
53     // will survive as part of the kid
54   }