If your address book contains a lot of entries, alphabetizing it might be convenient. You can easily do this by adding a
sort method to your
AddressBook class and by taking advantage of an
NSMutableArray method called
sortUsingSelector:. This method takes as its argument a selector that the
sortUsingSelector: method uses to compare two elements. Arrays can contain any type of objects in them, so the only way to implement a generic sorting method is to have you decide whether elements in the array are in order. To do this, you must add a method to compare two elements in the array.4 The result returned from that method is to be of type
NSComparisonResult. It should return
NSOrderedAscending if you want the sorting method to place ...