How to queue CKOperations for different CKDatabase - swift

Question

I create 2 operations, let's say CKModifySubscriptionsOperation. One is for private, another for shared database. I could queue them by adding to the OperationQueue, each next would start after previous completion block.
let operationQueue = OperationQueue()
operationQueue.maxConcurrentOperationCount = 1
// ...
operationQueue.addOperation(operation)
// Queued great but all subscriptions are created in private database
But I need to do some action (fetching, modifying etc) from different databases, but still need to queue them. Here is how I add operation to the database. How to put them to the single queue but still let them go to needed database each?
container.privateCloudDatabase.add(operation)
container.sharedCloudDatabase.add(operation)
// Put subscriptions to correct databases but no queue

Answer 1

I've solved the goal by creating a controlled custom operation.
Now we can queue cloud database specific operations just like that
let privateSubscriptionOperation = SubscriptionOperation(type: .private)
let sharedSubscriptionOperation = SubscriptionOperation(type: .shared)
operationQueue.addOperation(privateSubscriptionOperation)
operationQueue.addOperation(sharedSubscriptionOperation)
First of all, parent class
class CKDatabaseControlledOperation: Operation {
let databaseType: DatabaseType
let database: CKDatabase
private var _finished = false
private var _executing = false
init(type: DatabaseType) {
databaseType = type
switch type {
case .private:
database = CKContainer.default().privateCloudDatabase
case .shared:
database = CKContainer.default().sharedCloudDatabase
}
}
override var isExecuting: Bool {
get {
return !_executing
}
set {
willChangeValue(forKey: "isExecuting") // This must match the overriden variable
_executing = newValue
didChangeValue(forKey: "isExecuting") // This must match the overriden variable
}
}
override var isFinished: Bool {
get {
return _finished
}
set {
willChangeValue(forKey: "isFinished") // This must match the overriden variable
_finished = newValue
didChangeValue(forKey: "isFinished") // This must match the overriden variable
}
}
func stopOperation() {
isFinished = true
isExecuting = false
}
func startOperation() {
isFinished = false
isExecuting = true
}
enum DatabaseType: String {
case `private` = "private-changes"
case shared = "shared-changes"
}
}
And then we can create any database operation (subscription in this example but will work with any)
class SubscriptionOperation: CKDatabaseControlledOperation {
override func main() {
startOperation() //Operation starts
let subscription = CKDatabaseSubscription(subscriptionID: databaseType.rawValue)
//...set any needed stuff like NotificationInfo
let operation = CKModifySubscriptionsOperation(subscriptionsToSave: [subscription], subscriptionIDsToDelete: [])
operation.modifySubscriptionsCompletionBlock = { [unowned self] subscriptions, subscriptionIDs, error in
//Handle errors
self.stopOperation() //Operation ends
}
database.add(operation)
}
}