iOS: NSJSONSerialization results in "data paremeter is nil'

Question

I had the NSURLConnection and all the appropriate methods working in one view controller. Then i moved it to a UICollectionViewController and get an exception below

    - (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSError *jsonParsingError = nil;

//error right here!
    NSString
    *object = [NSJSONSerialization JSONObjectWithData:self.jsonReceivedData options:NSJSONReadingMutableContainers error:&jsonParsingError]; 

    if (jsonParsingError) {
        NSLog(@"JSON ERROR: %@", [jsonParsingError localizedDescription]);
    } else {
        NSLog(@"LIST: %@", object);
    }
}

The error is: * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'data parameter is nil'

Anyone have any ideas?

I suppose self.jsonReceivedData is not valid. Thats why it is not able to serialize. check your jsonReceivedData. — Nishant Tyagi, Apr 30 '13 at 06:40
It's great that you're using the error parameter, but the convention is to check the return value of the method is nil before looking at the error value. Cocoa methods only guarantee to have a valid error in such cases when the method returns nil. — Abizern, Apr 30 '13 at 06:53

score 11 · Accepted Answer · answered Apr 30 '13 at 06:41

11

The exception message is saying to you that the variable : self.jsonReceivedData is nil, and the method you are calling JSONObjectWithData do not support nil data ...

Initialize self.jsonReceivedData field to resolve the problem ;-) .

answered Apr 30 '13 at 06:41

aleroot

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you are correct, i forgot to do that when i moved code over. Stupid mistake on my part. Thanks! – Matthew Apr 30 '13 at 06:43

iOS: NSJSONSerialization results in "data paremeter is nil'

1 Answers1