CloudKit：在本地检查订阅

Question

在wwdc视频“CloudKit最佳实践”中，他们提到要检查如何“订阅更改”。这是他们展示的代码：

if (subscriptionIslocallyCached) {
    return
}
let subscription = CKDatabaseSubscription(subscriptionID: "shared-changes")
let notificationInfo = CKNotificationInfo()
notificationInfo.shouldSendContentAvailable = true
subscription.notificationInfo = notificationInfo
let operation = CKModifySubscriptionsOperation(
    subscriptionsToSave: [subscription], subscriptionIDsToDelete: [])

operation.modifySubscriptionsCompletionBlock = {
    if error != nil { } // Handle the error
    else { self.subscriptionIslocallyCached = true }

}

但他们没有提到定义“subscriptionIslocallyCached”的位置。你们中的任何人都知道如何定义“subscriptionIslocallyCached”？或者我如何初始化subscriptionIslocallyCached？

我真的很感谢你的帮助。