How do I "Look Me Up By Email" - ios

Question

I am making an iOS application and I would like to use the iCloud feature "Look Me Up By Email" found under iCloud in the Settings of iOS.
I would like to simplify the user experience by identifying users by their iCloud so they don't have to remember a login for my app.

Answer 1

As I understand this, this is a CloudKit feature related to CKDiscoverAllContactsOperation. You can discover people from your contacts with the same app and can be discovered by them. You need to request permission for that ability first, like this:
CKContainer.defaultContainer().requestApplicationPermission(CKApplicationPermissions.UserDiscoverability) { [unowned self] (status, error) -> Void in
//Your code handling error or success...
}
Note
Release notes for iOS 10 mention, that this operation and related functions will be changed. In iOS 10+ you need to use CKDiscoverAllUserIdentitiesOperation
Example of usage
init a container first, note that your container accountStatus must be correct
let container = CKContainer(identifier: "iCloud.com.YourContainerID")
Later, ask a permission
container.requestApplicationPermission(CKApplicationPermissions.userDiscoverability) { [unowned self] (status, error) -> Void in
if let err = error {
print(err)
}
else if status == CKApplicationPermissionStatus.granted{
//success
}
else{
print("Permission not granted")
print(status)
}
}
Later, you can get your current user record id and create a subscription for example (note that you don't need a permission and user record ID to create a subscription, but in my case it was needed to create a predicate):
container.fetchUserRecordID { [weak self] (recordID, error) in
let predicate = NSPredicate(format: "user = %#",userRecordID.recordName)
let subscription = CKSubscription(recordType: "myRecordType", predicate: predicate, options: CKSubscriptionOptions.firesOnRecordCreation)
container.publicCloudDatabase.save(subscription, completionHandler: { (subscription, error) in
//completion stuff here
}
}
Friends discoverability example
let discoverOperation = CKDiscoverAllUserIdentitiesOperation()
var users = [CKUserIdentity]()
discoverOperation.discoverAllUserIdentitiesCompletionBlock = { [weak self] (error: Error?) -> Void in
if let err = error as? NSError{
print("Discover Friends Error: \(err)")
} else {
//do whatever you want with discovered contacts
}
}
discoverOperation.userIdentityDiscoveredBlock = { (userIdentity: CKUserIdentity) -> Void in
users.append(userIdentity)
}
discoverOperation.queuePriority = Operation.QueuePriority.high //this option is up to your tasks
container.add(discoverOperation)