ios - JSON text did not start with array or object and option to allow fragments not set

Question

I'm sending this json response from server for a request to my IOS 7 app.

{
 "root": {
    "success": "1",
    "message": "Successfully retrieved data.",
    "data": {
        "records": [
            {
                "receipt_key": "xxxxxxxx",
                "receipt_id": "xxxxxxxx",
                "store_name": "xxxxxx",
                "amount": "xxxx",
                "date_purchase": "xxxxxxxx",
                "is_processed": "x",
                "created_on": "xxxxxxxx",
                "modified_on": "xxxxxxxx",
                "modified_on_millis": "xxxxxxxx",
                "user_folder": "xxxxxxxx",
                "category_id": "xxxxxxxx",
                "is_deleted": "x",
                "currency_id": "xxxxxxxx"
            }
        ]
    }
}
}

I use the following code for parsing the above json to NSDictionary object.

 NSMutableDictionary *json=[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];

But I'm getting this error on the above code.

Error Domain=NSCocoaErrorDomain Code=3840 "The operation couldn’t be completed. (Cocoa error 3840.)" (JSON text did not start with array or object and option to allow fragments not set.) UserInfo=0x8a8a700 {NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}

Answer 1

I ran into the same error when consuming a feed from a php page. Just as you encountered, the resulting json string passed a visual inspection, but would fail to serialize. My suspicion was that there was a hidden character somewhere the feed, so I converted each character to its unicode decimal equivalent and examined the results:

NSString *feedStr = [[NSString alloc] initWithData:feedData encoding:NSUTF8StringEncoding];
for(int i=0; i<[feedStr length]; ++i)
{
    unichar c = [feedStr characterAtIndex:i];
    NSLog(@"decimal char %d", c);
}

I found that before the first character and after the last was the character #65279. After a quick google search I found What is this char? 65279, where this was identified as a byte order mark.

In my case, I was able to fix this at the source by opening and saving all included php files, using a text editor that provided an option to use the "Encode in UTF-8 without BOM" encoding. For more info on the php side, see How to avoid echoing character 65279 in php?