iPhone crash with jsonData argument is NULL

iPhone client application crashed, when it received NULL as jsonData argument. Using third party JSONKit library, which has the following line of code:

- (id)objectWithData:(NSData *)jsonData error:(NSError **)error
{
  if(jsonData =开发者_StackOverflow= NULL) { [NSException raise:NSInvalidArgumentException format:@"The jsonData argument is NULL."]; }
  return([self objectWithUTF8String:(const unsigned char *)[jsonData bytes] length:[jsonData length] error:error]);
}

JSONKit documentation says:

Important: objectWithUTF8String: and mutableObjectWithUTF8String: will raise NSInvalidArgumentException if string is NULL.

Question: how should I handle this situation so that the iPhone application does NOT crash in this case? Not looking for theoretical exception handling code, but tips how do applications in general handle jsonData == NULL situation?

simple. abide by the library's rules, like so:

if (jsonData == nil) {
    assert(0 && "there was an error upstream -- handle the error in your app specific way");
    return; // not safe to pass nil as json data -- bail
}

// now we are sure jsonData is safe to pass

NSError * error = nil;
id ret = [json objectWithData:jsonData error:&error];
...

It's pretty clear, when there's no data, the library raises an exception (NSException). If you're unfamiliar with the terms of exception handling, I suggest reading about it on wikipedia, and then on Apple's Doc, it's a pretty common programming subject.

As far as the issue goes, you need to catch the exception:

@try
{
    // Do whatever you're doing with the JSON library here.
}
@catch (NSException *exception)
{
    // Something happend
    if ([exception.name isEqualToString:NSInvalidArgumentException])
    {
        // This must be the jsonData == NULL.
    }
}
@finally
{
    // Optional, you can clear things here.
}