Turning off iCloud and remove items from the ubiquitous container - ios

Question

I have a UISwitch in my app for users to switch on/off iCloud. I want to achieve the following: When a user turns off iCloud, all contents in the ubiquitous container will be removed and copied to a local directory as backups. However, as soon as the files have been removed from the ubiquitous container, copies on the iCloud server are also removed. This basically clear everything on iCloud.
I have the following questions:
How can files on the ubiquitous container be removed without affecting copies on the iCloud server?
What is the best or standard practice to remove files from the ubiquitous container before disabling iCloud?
Can iCloud be disabled at all after it has been initialised/enabled?
Thank you.

Answer 1

After reading Apple's documents and others suggestions, here is my understanding. I am not 100% sure if they are correct. Comments and corrections are most welcome:
Anything added to or removed from the ubiquity container will be synced with the iCloud server. The app has no control of this.
Once iCloud document storage has been enabled in Settings app by the user, it cannot be disabled by the app. The app's responsibility is to provide UI (assuming a UISwitch) to let user indicate where they want their documents synced with the iCloud for the app.
If the user turns off iCloud by turning off the UISwitch in the app (not in Settings), what the app should do is to stop querying metadata, stop listening to NSMetadataQueryDidUpdateNotification, and stop accessing files in the ubiquity container (as mentioned by crizzis above). If later the user turns iCloud on again, files already in the ubiquity container will be synced with iCloud automatically, and no manual merging should be needed unless unresolved conflicts occur.

Answer 2

Using evictUbiquitousItem(at url:)
See point #1. I'm not sure why you would want to do that, though. Can't you just stop accessing the local copies the second the switch is off?
I don't think it can be disabled programmatically. On a positive side, if you want to avail the users of a possibility to disable iCloud, it's already there. iCloud is supposed to be disabled via the Settings app, and all you really need to do is handle that fact within the app by listening to NSUbiquityIdentityDidChangeNotification
UPDATE
Amin Negm-Awad suggested that evictUbiquitousItem(at url:) forces a reload, and so the local copy is not permanently deleted. However, I've done a little testing just out of curiosity, and haven't found that to be the case. The following test:
func runTest(ubiURL: URL) {
self.query.searchScopes = [NSMetadataQueryUbiquitousDocumentsScope]
self.query.predicate = NSPredicate(format: "%K like '*'", NSMetadataItemFSNameKey)
NotificationCenter.default.addObserver(self, selector: #selector(self.metadataQueryDidUpdate(_:)), name: NSNotification.Name.NSMetadataQueryDidUpdate, object: self.query)
self.query.start()
self.query.enableUpdates()
let fileURL = ubiURL.appendingPathComponent("Documents/file.txt")
FileManager.default.createFile(atPath: fileURL.path, contents: "Hello".data(using: .utf8))
do {
try FileManager.default.startDownloadingUbiquitousItem(at: fileURL)
} catch {
print("startDownloadingUbiquitousItem: \(error.localizedDescription)")
}
}
var updateCount = 0
func metadataQueryDidUpdate(_ notification: Notification) {
print("######################")
print("update #\(updateCount)")
for file in query.results as! [NSMetadataItem] {
guard let fileURL = file.value(forAttribute: NSMetadataItemURLKey) as? URL, let fileStatus = file.value(forAttribute: NSMetadataUbiquitousItemDownloadingStatusKey) as? String else {
print("Invalid item!")
return
}
if fileStatus == NSMetadataUbiquitousItemDownloadingStatusCurrent {
print("URL to evict: \(fileURL)")
do {
try FileManager.default.evictUbiquitousItem(at: fileURL)
print("Eviction result: successful")
} catch {
print("evictUbiquitousItem: \(error.localizedDescription)")
}
}
print("File exists at URL: \(FileManager.default.fileExists(atPath: fileURL.path))")
}
updateCount = updateCount + 1
}
Yielded:
ubiURL is file:///private/var/mobile/Library/Mobile%20Documents/iCloud~com~example~blabla3/
######################
update #0
URL to evict: file:///private/var/mobile/Library/Mobile%20Documents/iCloud~com~example~blabla3/Documents/file.txt
evictUbiquitousItem: The file “file.txt” couldn’t be saved in the folder “blabla”.
File exists at URL: true
######################
...
update #3
URL to evict: file:///private/var/mobile/Library/Mobile%20Documents/iCloud~com~example~blabla3/Documents/file.txt
Eviction result: successful
File exists at URL: true
######################
update #4
File exists at URL: false
(no further updates followed)
I don't think the remote file will end up on the device unless startDownloadingUbiquitousItemAtUrl: is called with the evicted file's URL. Not sure if this behavior can be relied upon, though.