X-Git-Url: https://git.ralfj.de/rust-101.git/blobdiff_plain/5baae0ea037ed642b7fe8975fb3004b29827d5b1..c2e9145b487a8bd3d31c5a6f318c86aaf3f9d17d:/workspace/src/part12.rs?ds=inline diff --git a/workspace/src/part12.rs b/workspace/src/part12.rs index 23db4f6..390b5df 100644 --- a/workspace/src/part12.rs +++ b/workspace/src/part12.rs @@ -48,7 +48,7 @@ fn demo_cell(c: &mut Callbacks) { let count = Cell::new(0); // Again, we have to move ownership if the `count` into the environment closure. c.register(move |val| { - // In here, all we have is a shared borrow of our environment. But that's good enough for the `get` and `set` of the cell! + // In here, all we have is a shared reference of our environment. But that's good enough for the `get` and `set` of the cell! let new_count = count.get()+1; count.set(new_count); println!("Callback 2: {} ({}. time)", val, new_count); @@ -81,7 +81,7 @@ impl CallbacksMut { // We have to *explicitly* borrow the contents of a `RefCell` by calling `borrow` or `borrow_mut`. let mut closure = callback.borrow_mut(); // Unfortunately, Rust's auto-dereference of pointers is not clever enough here. We thus have to explicitly - // dereference the smart pointer and obtain a mutable borrow of the content. + // dereference the smart pointer and obtain a mutable reference to the content. (&mut *closure)(val); } } @@ -103,7 +103,6 @@ fn demo_mut(c: &mut CallbacksMut) { c.call(1); c.clone().call(2); } -// **Exercise 12.1**: Change the type of `call` to ask only for a shared borrow. Then write some piece of code using only the available, public -// interface of `CallbacksMut` such that a reentrant call to `call` is happening, and the program aborts because the `RefCell` refuses to hand -// out a second mutable borrow to its content. +// **Exercise 12.1**: Write some piece of code using only the available, public interface of `CallbacksMut` such that a reentrant call to a closure +// is happening, and the program panics because the `RefCell` refuses to hand out a second mutable borrow of the closure's environment.