iOS replaceObjectAtIndex Error

Question

I am new to iOS development, I encounter error when replaceObjectAtIndex. Any wrong with my codes? Please help.Thanks.

self.myArray =array;
for (NSDictionary *data in array) {
NSString *fbid = [data objectForKey:@"id"];

for (int index = 0; index < self.myPersonArray.count; index ++) {

    for (IP_PERSON *person in self.myPersonArray) {
        if ([person.UserDef2 isEqualToString:fbid]) {
            [self.myArray replaceObjectAtIndex:index withObject:person];
            break;
        }
    }
}

Error is : Terminating app due to uncaught exception NSGenericException, reason: '*** Collection <__NSArrayM: 0xa34f6c0> was mutated while being enumerated.

Don't make us play games to get information. **WHAT IS THE ERROR**? My guess is that it is *unrecognized selector*. — borrrden, Jul 17 '13 at 04:40

score 3 · Answer 1 · answered Jul 17 '13 at 04:44

3

You cannot use fast enumeration and mutate collection at the same time, hence the error message. You can resort to using an usual for-loop.

answered Jul 17 '13 at 04:44

Dmitry Shevchenko

31,814
10
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Sorry new here,Any example to refer.Thanks – Jason lau Jul 17 '13 at 04:47
Consider an example in this answer, the whole discussion is great too, http://stackoverflow.com/a/992910/7437 – Dmitry Shevchenko Jul 17 '13 at 04:48
am i missing something here? he *is* using the usual for loop, i don't see any fast enumeration.. – abbood Jul 17 '13 at 05:01
@abbood `self.myArray =array; for (NSDictionary *data in array)` – Dmitry Shevchenko Jul 17 '13 at 05:01
@DmitryShevchenko oh so that's the same as doing an enumerate object with block etc.. good to know.. – abbood Jul 17 '13 at 05:02
1

@abbood yep, this form is the *original* fast enumeration, block way just wraps around it. – Dmitry Shevchenko Jul 17 '13 at 05:13

score 0 · Answer 2 · answered Jul 17 '13 at 04:47

0

You're iterating over array, which is equal to self.myArray.

Further down, you're editing this array when you do: [self.myArray replaceObjectAtIndex:index withObject:person];

To resolve this, just make self.array a mutableCopy of the original array:

self.myArray = [array mutableCopy];

answered Jul 17 '13 at 04:47

ggmathur

833
5
12

Hi ggmathur, When I change to self.myArray = [array mutableCopy], I get the endless result.Do you know why ? Thanks Eg.1234,1234,1234,1234,1234,1234,1234.... – Jason lau Jul 17 '13 at 07:01

score 0 · Answer 3 · answered Jul 17 '13 at 04:47

You can take another temporary array and iterate over that array, so you are enumerating and mutating different array.

NSArray *tempArray = [yourArray copy];
for (IP_PERSON *person in tempArray) {
    if ([person.UserDef2 isEqualToString:fbid]) {
        [self.myArray replaceObjectAtIndex:index withObject:person];
        break;
   }
}
[tempArray release];

Alternatively you can iterate without an enumerator, you can use regular for loop with starting index, exit condition and increment as you have done in outer loop.

Syed Absar · Answer 4 · 2013-07-17T10:42:35.220

0

You can..

NSMutableDictionary *dictionary = [NSMutableDictionary dictionary]
self.myArray =array;
for (NSDictionary *data in array) {
NSString *fbid = [data objectForKey:@"id"];

                    for (int index = 0; index < self.myPersonArray.count; index ++) {

                        for (IP_PERSON *person in self.myPersonArray) {
                            if ([person.UserDef2 isEqualToString:fbid]) {
                                    [dictionary setObject:person forKey:@(index)]; //Notice this line
                                break;
                            }
                        }
                    }
                }

And then..

for(id key in dictionary) {
  [self.myArray replaceObjectAtIndex:[key intValue] withObject:[dictionary objectForKey:key]];
}

edited Jul 17 '13 at 10:42

answered Jul 17 '13 at 05:06

Syed Absar

2,274
1
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Hi Syed Absar, I following your code but I get the following error No visible @interface for 'NSMutableDictionary' declares the selector 'addObject:forKey:' – Jason lau Jul 17 '13 at 06:10
Sorry, it is setObject and not addObject. – Syed Absar Jul 17 '13 at 10:42

iOS replaceObjectAtIndex Error

4 Answers4