Question

I’ve done below code to try getting all contacts phone number from address book:

  ABAddressBookRef addressBook = ABAddressBookCreate();
  NSArray *arrayOfPeople = 
  (__bridge_transfer NSArray *)ABAddressBookCopyArrayOfAllPeople(addressBook);    
  NSUInteger index = 0;
  allContactsPhoneNumber = [[NSMutableArray alloc] init];

  for(index = 0; index<=([arrayOfPeople count]-1); index++){

    ABRecordRef currentPerson = 
    (__bridge ABRecordRef)[arrayOfPeople objectAtIndex:index];

    NSArray *phones = 
    (__bridge NSArray *)ABMultiValueCopyArrayOfAllValues(
    ABRecordCopyValue(currentPerson, kABPersonPhoneProperty));

    // Make sure that the selected contact has one phone at least filled in.
    if ([phones count] > 0) {
      // We'll use the first phone number only here.
      // In a real app, it's up to you to play around with the returned values and pick the necessary value.
      [allContactsPhoneNumber addObject:[phones objectAtIndex:0]];
    }
    else{
      [allContactsPhoneNumber addObject:@"No phone number was set."];
    }
  }

However, it works well in iOS 6 but not in iOS 5.
It got crash on following code:

ABRecordRef currentPerson = 
(__bridge ABRecordRef)[arrayOfPeople objectAtIndex:index];

The output prints:

*** Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFArray objectAtIndex:]: index (0) beyond bounds (0)'

Anyone has advice why it got crash? Thanks!

Answer 1

This is not an issue depending on iOS5/iOS6 but an issue with different testing environment. In once case (one simulator, I guess) you have contacts in your addressbook, in the other you don’t.

But your test in your for loop will fail for the case when [arrayOfPeople count] is zero, because count returns an NSUInteger, which is unsigned, and subtracting -1 to 0UL creates an underflow (as -1 interpreted as an unsigned integer gives you the maximum value of an integer instead, because -1 is negative and unsigned integers can only store positive integers of course).

So when you don’t have any contact and [arrayOfPeople count] is zero, you are entering into your for loop anyway thus the crash when trying to get the object at index 0 in your empty array of people.

---

Replace your condition in your for loop from

for(index = 0; index<=([arrayOfPeople count]-1); index++)

To

for(index = 0; index<[arrayOfPeople count]; index++)

And your crash should go away as you won’t underflow and won’t enter in your for loop when you don’t have any contact in your addressbook.