[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.

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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.

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This is my code, easy for understand.

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

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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";