[Objective-C]NSDictionary dictionaryWithObjectsAndKeys: lost content

if we have a custom data object 'Question *obj' and initial a NSDictionary with obj
NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                      [NSNumber numberWithInteger:obj.value1], @"QuestionNo",
                      obj.value2, @"QuestionKind",
                      obj.value3, @"Question",
                      nil];

The above 'dict' has 3 key/value pairs in most time.
But, dict may lost the content(less than 3 pairs) if the 'Question *obj' has nil value.
Because [NSDictionary dictionaryWithObjectsAndKeys:] stops to add objects when it finds a nil value.