How can I implement the observer pattern in Rust?

Question

I have an observable collection and an observer. I want the observer to be a trait implementation of trait Observer. The observable object should be able to not

Answer 1

I used a callback function. It's simple and powerful and there are no lifetime issues or type erasure.

I tried Weak, but

1. It needs an Rc
2. You have to repeat code to create a different observer struct.
3. It requires type erasure

pub struct Notifier {
    subscribers: Vec>,
}

impl Notifier {
    pub fn new() -> Notifier {
        Notifier {
            subscribers: Vec::new(),
        }
    }

    pub fn register(&mut self, callback: F)
    where
        F: 'static + Fn(&E),
    {
        self.subscribers.push(Box::new(callback));
    }

    pub fn notify(&self, event: E) {
        for callback in &self.subscribers {
            callback(&event);
        }
    }
}