check if NSNumber is empty

Question

How do I check if a NSNumber object is nil or empty?

OK nil is easy:

NSNumber *myNumber;
if (myNumber == nil)
    doSomething

But if the object has been created, but there is no value in it because an assignment failed, how can I check this? Use something like this?

if ([myNumber intValue]==0)
   doSomething

Is there a general method for testing objects on emptiness like for NSString available (see this post)?

Example 1

NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
[dict setValue:@"" forKey:@"emptyValue"];
NSNumber *emptyNumber = [dict objectForKey:@"emptyValue"];

Which value does emptyNumber contain? How can I check if emptyNumber is empty?

Example 2

NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
[dict setValue:@"" forKey:@"emptyValue"];
NSString *myString = [dict objectForKey:@"emptyValue"];
if (myString == nil || [myString length] == 0)
    // got an empty value
    NSNumber *emptyNumber=nil;

What happens if I use this after emptyNumber was set to nil?

[emptyNumber intValue]

Do I get zero?

Example 3

NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
[dict setValue:@"" forKey:@"emptyValue"];
NSNumber *myEmptyValue = [dict objectForKey:@"emptyValue"];
if (myEmptyValue == nil)
    // NSLog is never called
    NSLog(@"It is empty!");

Like this way NSLog is never called. myEmptyValue is not nil and not NSNull. So it contains an arbitrary number?

check if NSNumber is empty

5 Answers