NSUserDefaultsをデータを取得する

TestController.m


   NSUserDefaults *uds = [NSUserDefaults standardUserDefaults]; 
   NSMutableArray *arr =[uds mutableArrayValueForKey:@"save_songs"];

NSUserDefaultsにデータを保存

TestController.m


    NSUserDefaults *uds = [NSUserDefaults standardUserDefaults];  
    [uds setObject:_arr forKey:@"save_songs"];

NSUserDefaultsをデータの中身を削除する

TestController.m


   NSString *appDomain = [[NSBundle mainBundle] bundleIdentifier];
    [[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];