CKQuerySubscription:未能进行订阅

我有一个iOS应用程序正在使用中 云工具包 . 我想订阅。

import CloudKit

class HomeViewController: UIViewController {
    override func viewDidLoad() {
        registerSubscription()
    }

    func registerSubscription() {
        let cloudContainer = CKContainer(identifier: "iCloud.com.xxx.XXXXX")
        let privateDB = cloudContainer.privateCloudDatabase
        let predicate = NSPredicate(format: "TRUEPREDICATE") // TRUEPREDICATE: all records of the specified type match the predicate
        let subscription = CKQuerySubscription(recordType: "PrivateRecords", predicate: predicate, options: .firesOnRecordCreation)
        privateDB.save(subscription, completionHandler: ({returnRecord, error in
            if let err = error {
                print("Subscription has failed: \(err.localizedDescription)")
            } else {
                print("Subscription set up successfully")
                print("Subscription ID: \(subscription.subscriptionID)")
            }
        }))
    }
}

具有nil通知信息的订阅:CKQuerySubscription:0x7fd7bfca7ec0;;查询订阅:recordType=PrivateRecords,predicate=TRUEPREDICATE,subscriptionOptions=1,subscriptionID=728863F8-3852-4A12-B5C6-F65EC945207A,zoneID=(null)

我可以根据订阅ID删除订阅。但每次运行此应用时,它都会为我提供不同的ID。事实上,我对一个 应用程序。它有订阅。另外,我在一周前删除了一个订阅类型,看看会发生什么。我真的不知道订阅ID是用来做什么的。

那么我在订阅时做错了什么呢?谢谢。