pub fn call(&mut self, val: i32) {
        // Since they are of type `FnMut`, we need to mutably iterate.
        for callback in self.callbacks.iter_mut() {
            unimplemented!()
        }
    }
// And here we call all the stored callbacks.
And here we call all the stored callbacks.
And here we call all the stored callbacks .
pub fn call(&mut self, val: i32) {
        // Since they are of type `FnMut`, we need to mutably iterate.
        for callback in self.callbacks.iter_mut() {
            unimplemented!()
        }
    }
pub fn call ( & mut self , val : i32 ) { // Since they are of type `FnMut`, we need to mutably iterate. for callback in self . callbacks . iter_mut ( ) { unimplemented ! ( ) } }
And here we call all the stored callbacks.
And here we call all the stored callbacks .
&mut self
val
i32