How to differentiate the returned value of a function in Objective C?

I have a function that gives 2 different String values that are returned :

-(NSString*)load:(NSDictionary *)dict
{

    NSDictionary *dataDict = [self objectForId:@"data" fromDict:dict withDefault:nil];
    if (dataDict) {
        NSDictionary *success = [self objectForId:@"success" fromDict:dataDict withDefault:nil];

        NSString *str = [NSString stringWithFormat:@"%@", success];

        if ([str isEqualToString: @"1"])
        {
            NSDictionary *idDict = [self objectForId:@"id" fromDict:dataDict withDefault:nil];
            if (idDict) {
                NSString *idString = [NSString stringWithFormat:@"%@", idDict];
                return idString;
            }

        } else {
            NSDictionary *messages = [self objectForId:@"messages" fromDict:dataDict withDefault:nil];
            if (messages) {
                NSDictionary *messageDict = (NSDictionary *)messages;
                NSArray *type = messageDict[@"type"];
                if (type.count > 0) {
                    NSString *messageString = type[0][@"message"];
                    return messageString;
                }
            }
        }
    }
    return  nil;
}

And accessing the stringValue like this :

 NSString *string = [className load:dict];

Now I want to write if else statements for "idString" and "messageString" return values. How do I differentiate the 2 return values?