[NSNull isEqualToString:]: unrecognized selector sent to instance

try to compare a field returned by web-service and which contains only either the String true or false (YES, it's STRING and not boolean), so i try to compare it with another string like this :

if ([withOptions isEqualToString:@"true"]) {
               annotation.stationLavage=@"with";
           }else {
开发者_JS百科               annotation.stationLavage=@"without";
           }

so when withOptions string contains the "true" string, all is ok, and when it contains the "false" string i got this exception in the log :

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSNull isEqualToString:]: unrecognized selector sent to instance 0x2984d68'

i am pretty sure that in all cases, withOptions contains a string value (either "true" or "false") and it never contains NULL.

i am pretty sure that in all cases, withOptions contains a string value (either "true" or "false") and it never contains NULL.

Clearly, that assumption is wrong. :)

On the line before that if() statement, add NSLog(@"%@ - %@", withOptions, [withOptions class]);

Not that NSNull and NULL are not the same thing; NSNull is a class whose singleton instance represents "no value" in containers (and other things) that don't accept nil as values.

When that crash occurs, withOptions is referring to an instance of NSNull.

This is my code, easy for understand.

if ([[info objectForKey:@"address"] isKindOfClass:[NSNull class]]) {
            dto.address    =   @"Unknown";
}

If you want to do a safe comparaison and your are not 100% that your "withOption" contains a string , because it could be null for instance (the case where no option has been given) you could do this:

if ([@"true" isEqualToString:withAnnotation]) {
     annotation.stationLavage=@"with";
 }else {
     annotation.stationLavage=@"without";
 }

Note that you can even shorten the comparaison:

annotation.stationLavage=[@"true" isEqualToString:withAnnotation]?@"with":@"without";