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];