/LHL-CloudKit-Intro

Lighthouse Labs Lecture on CloudKit

Primary LanguageSwift

build-lists: true

[fit]CloudKit

[fit]What is CloudKit?

  • Apple's backend solution.
  • Powers iCloud.
  • Some cool apps using it, like Things 3.
  • Backend without having to set one up.
  • Passes cost on to the user.
  • Easy Authentication & Setup.

[fit]Parts of CloudKit

[fit]CKContainer

  • There is one default CloudKit Container per app.
  • The default container's identifier matches that of the app's bundle id.
  • Apps can have multiple containers and apps can share containers with other apps by the same developer.

[fit]CKDatabase

  • CKDatabase objects are children of CKContainer objects.
  • Each container holds multiple databases.
  • They have a public database accessible to all users. (Readonly for users not signed in to iCloud).
  • Your app can also read/write to the user's private database. (Requires active iCloud account).

More...

  • Private data is not visible to developers in the dashboard.
  • New in iOS 10 is the "shared database". (Requires active iCloud account).
  • The shared database, like the private database, is not visible in the dashboard to developers.
  • Shared data access is controlled by an CKShare object.
  • Users are on the hook for private data storage, which is good for developers. Cost details.

[fit]CKRecord

  • CKRecords are children of CKDatabase objects.
  • Think of them as corresponding to database rows.
  • These records are essentially key-value dictionaries.
  • Data types are limited to: NSString, NSNumber, NSData, NSDate, NSArray, CLLocation, CKAsset, CKReference.
  • NSData should only be used for binary data of a few kilobytes.
  • Use CKAsset for binary files that are larger than a few kilobytes.
  • CKReference creates a backlink to related record by storing the id of the target object.
  • CKReference supports cascade deletion.
  • 1 to many relationships are supported.
  • A single record is limited to 750 references.
  • Records require a zone (CKRecordZone).
  • If you don't assign a zone then the default zone will be used.
  • CKRecordZones are used to further encapsulate data. (Be careful).

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[fit]CKQuery

  • Used to control you fetch operations.
  • Can only be used with a single RecordType.
  • You make a CKQuery using NSPredicate. Full Predicate construction isn't supported. (Check the documentation).
  • Set NSPredicate with a value of true to get all records.
  • CKQuery also takes an optional NSSortDescriptor array.

[fit]Authentication

  • If your user is logged into iCloud they are authenticated!
  • If not, they can only read the public db.
  • Always check that users are logged into iCloud and warn them of limited functionality if they aren't.
  • Call accountStatus(completionHandler:) on the container to determine whether the user is logged in.
  • Your app should sign up to receive CKAccountChanged notifications.

[fit]CKReference

  • Used to create a many-to-one relationship between records in a database.
  • A reference stores information about the one record that is the target of the reference.
  • The reference object is saved in the fields of one or more records to create a link from those records to the target.
  • Both records must be located in the same zone.
  • For instance, let's say our employee has a department.
  • Make a CKReference out of a department record.
  • department is the target object.
  • We then add this reference (backlink) to any employee objects that are in that department.
  • When creating a CKReference we have to specify the "delete policy".
  • If the target object is deleted (department in our example) does this remove all employees in that department or not?

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[fit]Convenience Vs Operations API

  • There are 2 API's: Convenience, Operations.
  • CloudKit Operations derive from (NS)Operation.
  • Operations let you batch fetches and changes.
  • Operations are highly configurable. Eg. (dis)allow cellular, fetch partial records, limit result set, progress reporting, determining priority, etc.

[fit]Operations

[fit]CKQueryOperation

  • Used when you have a lot of data.
  • CKQueryOperation is used for performing fetches and allows you to specify a result size, to permit paging, and get progress.
  • Since CKOperation inherits from NSOperation you may have to look at the NSOperation class to figure out how to use it.

[fit]CKModifyRecordsOperation

  • An operation that saves changes to one or more record objects.
  • Used for add, update, delete operations.
  • The savePolicy determines how you want to handle conflicting data.
  • Modify operations can be marked isAtomic if we want all operations to fail if any single record fails. (true default)
  • Assign a completion block to handle callbacks.

[fit]Demo

[fit]Push Notifications

  • No encryption key setup required.
  • Push notifications can be silent or not.
  • Silent notifications do not require user authorization. Just call registerForRemoteNotifications on UIApplication.
  • Push notifications can only be received on a real device.
  • Uses UNUserNotification API!

[fit]CKSubscription

  • You can subscribe to data changes to receive push notifications!
  • Only create a CKSubscription once. (You can store this in UserDefaults)
  • These can run silently and wake the app in the background to update data.
  • Typically you will fetch when you're notified about changes.

More...

  • To receive push notifications as silent set the CKNotificationInfo instance to shouldSendContentAvailable to true.
  • CKDatabaseSubscription (iOS 10+) only works on private + shared databases and allows you to be notified of changes across the db.
  • Make sure to set the notificationInfo property on the subscription instance.

More...

  • Use the application(_: didReceiveRemoteNotification: fetchCompletionHandler:) to receive your notification callback.
  • Inside the completion handler pass the userInfo key to a CKNotification(fromRemoteNotificationDictionary:) in order to check the subscriptionID.

[fit]Push Demo

References