Setting worldView to nil


In the documentation for MKMapViewDelegate Protocol under Overview it says

Why did we not do this in dealloc as we did with locationManger? Do we not have to worry about it if the delegate is set in the UI as opposed to programmatically as we did with locationManager?

Similarly for locationTitleField. In the help for UITextField Class Reference under delegate it says

Since this has the attribute assign which I believe is equivalent to __unsafe_unretained in this case does this need to be set to nil also?