NSJSONSerialization results in EXC_BAD_ACCESS

Question

Currently I am writing an app (Target iOS 6, ARC enabled) that uses JSON for data transmission and Core Data for persistent storage. The JSON data is generated out of a MySQL database by a PHP script via json_encode.

My Problem is that with data from certain tables the following code fails:

- (NSDictionary *)executeFetch:(NSString *)query
{
    NSURL *requesturl = [NSURL URLWithString:[query stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

    NSError *dataError = nil;
    self.jsonData = [NSData dataWithContentsOfURL:requesturl options:kNilOptions error:&dataError];

    NSError *error = nil;
    self.jsonSerializationResult = [NSJSONSerialization JSONObjectWithData:self.jsonData options:NSJSONReadingMutableContainers|NSJSONReadingMutableLeaves error:&error];

    return self.jsonSerializationResult;

}

The program always crashes with an EXC_BAD_ACCESS error on the line where it says self.jsonSerializationResult and Instruments says that there was a Zombie detected. I know that this means that some object I send a message to is nil, but I can't find out how to fix it... That's what Instruments has to say:

#   Address Category    Event Type  RefCt   Timestamp   Size    Responsible Library Responsible Caller
0   0xa1b8a70   CFString (mutable)  Malloc  1   00:01.603.081   32  Foundation  -[NSPlaceholderMutableString initWithBytesNoCopy:length:encoding:freeWhenDone:]
1   0xa1b8a70   CFString (mutable)  Release 0   00:01.603.137   0   Foundation  newJSONValue
2   0xa1b8a70   CFString (mutable)  Zombie  -1  00:01.603.259   0   Foundation  newJSONString

My program works with every JSON output except for this one:

{
   "termin":[
      {
         "termin_id":"17",
         "veranstaltung_id":"20",
         "beginn":"2012-09-28 17:00:00",
         "ende":"2012-09-28 18:00:00",
         "freie_pl\u00e4tze":null
      },
      {
         "termin_id":"18",
         "veranstaltung_id":"26",
         "beginn":"2012-09-28 19:00:00",
         "ende":"2012-09-28 20:00:00",
         "freie_pl\u00e4tze":null
      },
      {
         "termin_id":"19",
         "veranstaltung_id":"26",
         "beginn":"2012-09-28 21:00:00",
         "ende":"2012-09-28 22:00:00",
         "freie_pl\u00e4tze":null
      },
      {
         "termin_id":"20",
         "veranstaltung_id":"46",
         "beginn":"2012-09-28 19:00:00",
         "ende":"2012-09-28 20:00:00",
         "freie_pl\u00e4tze":null
      },
      {
         "termin_id":"24",
         "veranstaltung_id":"66",
         "beginn":"2012-09-28 22:00:00",
         "ende":"2012-09-28 22:30:00",
         "freie_pl\u00e4tze":"120"
      }
   ]
}

I thought about some possible error sourced but none seems to be the responsible:

jsonData or jsonSerializationResult could be nil: they aren't
PHP generated invalid JSON: checked for that with a validator
null Values: not a problem with other tables

Has anybody got an idea?

score 11 · Accepted Answer · edited May 23 '17 at 12:24

11

It looks like a bug/shortcoming with NSJSONSerialization. The problem is caused by the escaped unicode characters (freie_pl\u00e4tze instead of freie_plätze). You have two options -

Convert the escaped Unicode to real Unicode characters. Try this SO answer
Use another JSON engine, such as JSONKit. JSONKit also claims to be more performant than NSJSONSerialization.

edited May 23 '17 at 12:24

Community

1
1

answered Oct 11 '12 at 15:43

user1071136

15,636
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Thank you very much! That was the only thing I didn't alter while examining the differences between the failing data and the working one... Surprisingly the escaped characters only seem to be a problem for the dictionary keys, not for the values... – Christian Hennen Oct 11 '12 at 16:30
BTW, I'm only seeing this if I use the `NSJSONReadingMutableContainers | NSJSONReadingMutableLeaves` options. Is this your experience, too? – Rob Sep 10 '13 at 16:24
Hello from `AFNetworking` code comments. :) Thank you, it really helps! – skywinder Feb 09 '14 at 23:58
I have been using JSONKit for years. Now the project is almost dead (last update was 2 years ago). Des this Apple's NSJSONSerialization was fixed? Which alternatives so far? TouchJSON is used by Facebook SDK. – loretoparisi Apr 14 '14 at 23:25
1

Escaped unicode characters has been fixed for `NSJSONSerialization` in iOS 7, see http://openradar.appspot.com/radar?id=2397401#ag9zfm9wZW5yYWRhci1ocmRyFAsSB0NvbW1lbnQYgICAgIDdwwgM – 0xced Dec 30 '15 at 22:04

score 4 · Answer 2 · answered Dec 03 '12 at 13:20

I know this question has been answered but I think some beginners may have the same issue as me and be brought to this question.

The EXC_BAD_ACCESS message was caused by malformed JSON. As I had accidentally used the same name for an Object which causes issues when converting the JSON into a dictionary.

Annoyingly it didn't bring up a formatting error. Here is an example of the JSON that caused the issue:

"levels" : {
    "level1": {
        ....
    },
    "level1": {
        ... << All objects should have different names. This should be called level2.
    },
    "level3": {
        ...
    }

To fix the issue I had to ensure that all objects of the same level had different names.

score 1 · Answer 3 · answered Apr 24 '14 at 16:40

Just tested NSJSONSerialization today. With iOS 7.1. It is working. No issue found. Looks like Apple fixed the issue.

NSString* jsonString = @"{ \"freie_pl\\u00e4tze\":null}";

NSData* jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];

NSError *error = nil;
NSDictionary* jsonSerializationResult = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers|NSJSONReadingMutableLeaves error:&error];

NSLog(@"%@", jsonSerializationResult);

NSJSONSerialization results in EXC_BAD_ACCESS

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