diff options
Diffstat (limited to 'src/doc/book/listings/ch15-smart-pointers/listing-15-29/src/main.rs')
-rw-r--r-- | src/doc/book/listings/ch15-smart-pointers/listing-15-29/src/main.rs | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/src/doc/book/listings/ch15-smart-pointers/listing-15-29/src/main.rs b/src/doc/book/listings/ch15-smart-pointers/listing-15-29/src/main.rs new file mode 100644 index 000000000..ea13df0eb --- /dev/null +++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-29/src/main.rs @@ -0,0 +1,54 @@ +use std::cell::RefCell; +use std::rc::{Rc, Weak}; + +#[derive(Debug)] +struct Node { + value: i32, + parent: RefCell<Weak<Node>>, + children: RefCell<Vec<Rc<Node>>>, +} + +// ANCHOR: here +fn main() { + let leaf = Rc::new(Node { + value: 3, + parent: RefCell::new(Weak::new()), + children: RefCell::new(vec![]), + }); + + println!( + "leaf strong = {}, weak = {}", + Rc::strong_count(&leaf), + Rc::weak_count(&leaf), + ); + + { + let branch = Rc::new(Node { + value: 5, + parent: RefCell::new(Weak::new()), + children: RefCell::new(vec![Rc::clone(&leaf)]), + }); + + *leaf.parent.borrow_mut() = Rc::downgrade(&branch); + + println!( + "branch strong = {}, weak = {}", + Rc::strong_count(&branch), + Rc::weak_count(&branch), + ); + + println!( + "leaf strong = {}, weak = {}", + Rc::strong_count(&leaf), + Rc::weak_count(&leaf), + ); + } + + println!("leaf parent = {:?}", leaf.parent.borrow().upgrade()); + println!( + "leaf strong = {}, weak = {}", + Rc::strong_count(&leaf), + Rc::weak_count(&leaf), + ); +} +// ANCHOR_END: here |