if (![defaults objectForKey:@"obj"]) {
    difficultyLabel.text = @"Difficulty: Easy";
    [defaults setObject:@"Easy" forKey:@"obj"];
} else {
    difficultyLabel.text = [NSString stringWithFormat:@"Difficulty: %@", [defaults objectForKey:@"diff"]];
}

if ([label.text isEqualToString:@"Difficulty: Easy"]) {
            label.text = @"Difficulty: Hard";
            [defaults setObject:@"Hard" forKey:@"obj"];
            NSLog(@"%@",[defaults objectForKey:@"obj"]);

        } else {
            label.text = @"Difficulty: Easy";
            [defaults setObject:@"Easy" forKey:@"obj"];
            NSLog(@"%@",[defaults objectForKey:@"obj"]);

NSString * str = @"name123";
NSUserDefaults *def=[NSUserDefaults standardUserDefaults];
[def setObject:str forKey:@"Key"];
[def synchronize];
NSLog(@"str = = %@",str);

NSUserDefaults *def=[NSUserDefaults standardUserDefaults];
NSString *str2 = [def valueForKey:@"Key"];
NSLog(@" Saved str  = = %@",str2);