Question

I have the following code in a loop

   NSArray * images = [definitionDict objectForKey:@"Images"];
    NSLog(@"images in definitionDict %@", images);
    if (!images )
        NSLog(@"NULL");
    else
        NSLog(@"NOTNULL");

which gives the following outputs

images in definitionDict (
    "/some/brol/brol.jpg"
)
NOTNULL
images in definitionDict <null>
NOTNULL

I do not understand the second case, where the images array is null. Why is this not detected correctly in my test ? How can I debug such a problem ?

Answer 1

<null> is not nil. nil will print (null) when printed. What you have is an NSNull. NSNull IS an object, it just doesn’t respond to much. Its available as a placeholder for you to use.

To test for NSNull you can use if ([images isEqual:[NSNull null]])

See the docs for more info on NSNull