CLLocationManager, MKReverseGeocoder, cleaning up memory

In the More iPhone 3 development book, after the author is done with the locationManager delegate method of getting updates, he puts this at the end of that method:

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {

    // some code here

    manager.delegate = nil;
    [manager stopUpdatingLocation];
    [manager autorelease];    
}开发者_JAVA技巧

And similarly, in the MKReverseGeocoder delegate methods, when he's done he does this:

- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFindPlacemark:(MKPlacemark *)placemark {

    //some code here

    geocoder.delegate = nil;
    [geocoder autorelease];
}

Why do you need to do that in order to clean up memory? I thought the rule was if you alloc/init it, you need to release it. Why does he add the locationManager and geocoder to the autorelease pool? Thanks.

This is done to avoid calling the delegate methods

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation

or

- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFindPlacemark:(MKPlacemark *)placemark

when you dealloc the object that responds to those CLLocationManager/MKReverseGeocoder protocols