NSDictionary check for null

Question

Is there a quick method for determining if a value is NSNULL in a dictionary without checking for that objects class like

[[dict objectForKey:@"foo"] class] != [NSNull null];

Answer 1

Actually what you have posted is not correct , you are comparing class ( NSNull ) to the singleton instance of this class ( NSNull null ) ,

the correct would be

[[dict objectForKey:@"foo"] isKindOfClass:[NSNull class]];

or comparing the instances

[dict objectForKey:@"foo"] == [NSNull null];

but if you have lots of this calls , you can create a category of NSDictionary and add method there , something like

- (BOOL)nl_isNSNullAt:(id)key {
    return [[self objectForKey:key] isKindOfClass:[NSNull class]];
}

or with instances

- (BOOL)nl_isNSNullAt:(id)key {
    return [self objectForKey:key] == [NSNull null];
}

then you can directly access

[dict nl_isNSNullAt:@"foo"]

You can of course choose the name of the method and category ...