Core data - Check for null - iOS - ios

Question

On entering a new data into my core data for my given entity, how do I check if the entry for a particular attribute is null?
I have three attribute
name, mail and mailedCustomer.
I add data as follows:
SalesPerson *data = (SalesPerson *)[NSEntityDescription insertNewObjectForEntityForName:#"SalesPerson" inManagedObjectContext:self.managedObjectContext];
[data setName:name];
[data setEmail:userEmail];
NSLog(#" mailed personel%#",data.mailedCustomer);
if([data.mailedCustomer != nil){
NSLog(#"inside condition");
[data setMailedCustomer:#"//"];
}
This doesn't work for me. Im trying to append some strings. So when I enter for the first time I need that attribute to be #"//" then append on further calls.
NSLog(#" mailed personnel %#",data.mailedCustomer);
The above NSLog gives me:
mailed personnel (null)

Answer 1

If I get what you want, your if statement is incorrect. You're now checking if it's NOT nil (meaning it has some value), and then you're resetting it to //. If you want it to be // and then append values, you have to check if it IS nil and then set it to //:
if (!data.mailedCustomer) {
NSLog(#"inside condition");
[data setMailedCustomer:#"//"];
}

Answer 2

#interface NSObject (PE)
- (BOOL) isNull:(NSObject*) object;
- (BOOL) isNotNull:(NSObject*) object;
#end
#implementation NSObject (PE)
- (BOOL) isNull:(NSObject*) object {
if (!object)
return YES;
else if (object == [NSNull null])
return YES;
else if ([object isKindOfClass: [NSString class]]) {
return ([((NSString*)object) isEqualToString:#""]
|| [((NSString*)object) isEqualToString:#"null"]
|| [((NSString*)object) isEqualToString:#"<null>"]);
}
return NO;
}
- (BOOL) isNotNull:(NSObject*) object {
return ![self isNull:object];
}
#end
if([self isNotNull:some object])
{
not null
}
else
{
null
}