iOS 远程推送注册的小问题

#ifdef __IPHONE_8_0
    // 在 iOS 8 下注册苹果推送，申请推送权限。
    
    UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:(UIUserNotificationTypeBadge
                                                                                         |UIUserNotificationTypeSound
                                                                                         |UIUserNotificationTypeAlert) categories:nil];
    [[UIApplication sharedApplication] registerUserNotificationSettings:settings];
#else
    // 注册苹果推送，申请推送权限。
    [[UIApplication sharedApplication] registerForRemoteNotificationTypes:UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeAlert | UIRemoteNotificationTypeSound];
#endif