CODEWITHSUNDEEP
iphonejson
JOM
JOM

Reputation: 8207

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 == 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?

Upvotes: 3

Views: 1181

Answers (2)

justin
justin

Reputation: 104708

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];
...

Upvotes: 6

Can
Can

Reputation: 8571

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.
}

Upvotes: 0

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