//@ (There's not even an automatic derivation happening for the cases where it would be possible.)
//@ This restriction propagates up to `Callbacks` itself. What could we do about this?
+//@ ## `Rc`
//@ The solution is to find some way of cloning `Callbacks` without cloning the environments. This can be achieved with
//@ `Rc<T>`, a *reference-counted* pointer. This is is another example of a smart pointer. You can `clone` an `Rc` as often
//@ as you want, that doesn't affect the data it contains. It only creates more references to the same data. Once all the
impl Callbacks {
pub fn new() -> Self {
- Callbacks { callbacks: Vec::new() } /*@*/
+ Callbacks { callbacks: Vec::new() }
}
// Registration works just like last time, except that we are creating an `Rc` now.
pub fn call(&self, val: i32) {
// We only need a shared iterator here. Since `Rc` is a smart pointer, we can directly call the callback.
for callback in self.callbacks.iter() {
- callback(val); /*@*/
+ callback(val); /*@*/
}
}
}
impl CallbacksMut {
pub fn new() -> Self {
- CallbacksMut { callbacks: Vec::new() } /*@*/
+ CallbacksMut { callbacks: Vec::new() }
}
pub fn register<F: FnMut(i32)+'static>(&mut self, callback: F) {
- let cell = Rc::new(RefCell::new(callback));
+ let cell = Rc::new(RefCell::new(callback)); /*@*/
self.callbacks.push(cell); /*@*/
}