Collection <__NSCFString:> was mutated while being enumerated crash

Question

For some reason, I am getting a crash (noted below) saying "Collection <__NSCFString: 0x155cefd0> was mutated while being enumerated", but only on an actual device. It works on the Xcode test device. I'm not entirely sure what that means, so how do I approach this lldb crash?

ABAddressBookRef addressBookRef = ABAddressBookCreateWithOptions(NULL, nil);
        ABRecordRef pet = ABPersonCreate();
        ABRecordSetValue(pet, kABPersonFirstNameProperty, (__bridge CFStringRef)petFirstName, nil);
        ABRecordSetValue(pet, kABPersonLastNameProperty, (__bridge CFStringRef)petLastName, nil);

        ABMutableMultiValueRef phoneNumbers = ABMultiValueCreateMutable(kABMultiStringPropertyType);
        ABMultiValueAddValueAndLabel(phoneNumbers, (__bridge CFStringRef)petPhoneNumber, kABPersonPhoneMainLabel, NULL);
        ABRecordSetValue(pet, kABPersonPhoneProperty, phoneNumbers, nil);

        ABAddressBookAddRecord(addressBookRef, pet, nil);

        NSArray *allContacts = (__bridge NSArray *)ABAddressBookCopyArrayOfAllPeople(addressBookRef);
        for (id record in allContacts){
            ABRecordRef thisContact = (__bridge ABRecordRef)record; //*******The line below is where the crash is occurring*********   
            if (CFStringCompare(ABRecordCopyCompositeName(thisContact),
                                ABRecordCopyCompositeName(pet), 0) == kCFCompareEqualTo){
                //The contact already exists!
                //detects if duplicate

                return;
            }
        }

Is that the exact code or do you attempt to delete the dupe or some such? — Hot Licks, May 15 '14 at 18:16
And are you sure `allContacts` is an NSArray? The message kind of suggests that it's a NSString. — Hot Licks, May 15 '14 at 18:17
It fails only on an actual device. It works on the test device. I'll add that to the question. — user3642059, May 15 '14 at 18:22
This code looks like it is leaking memory. `ABRecordCopyCompositeName` will return a `CFStringRef` that you need to release, you'll need to save these in separate variables so that you can release them after the compare. — James Snook, May 15 '14 at 18:33
Interesting, so how would I fix something like that. [ABRecordCopyCompositeName release];? — user3642059, May 15 '14 at 18:37
It's because I disabled arc. Unfortunately, I have to disable arc to use nsxml. So how do I go about doing this without arc? — user3642059, May 15 '14 at 19:01

score 0 · Answer 1 · answered May 15 '14 at 18:26

You are changing a collection at some other point of your application. According to Apple docs "It is not safe to remove, replace, or add to a mutable collection’s elements while enumerating through it"
Please check the following:

Which collections are you working with in your app, that could be modify while your above code is running.
If you need to modify any collection while iterating through it, use suggested techniques in linked docs.

Collection <__NSCFString:> was mutated while being enumerated crash

1 Answers1