CKDatabase

An app container has a public database whose data is accessible to all users and a private database whose data is accessible only to the current user. A database object takes requests for data and applies them to the appropriate part of the container.

You do not create database objects yourself, nor should you subclass CKDatabase. Your app’s CKContainer objects provide the CKDatabase objects you use to access the associated data. Use database objects as-is to perform operations on data.

The public database is always available, regardless of whether the device has an active iCloud account. When no iCloud account is available, your app may fetch records and perform queries on the public database, but it may not save changes. (Saving records to the public database requires an active iCloud account to identify the owner of those records.) Access to the private database always requires an active iCloud account on the device.

You interact with database objects as follows:

• Assign a database object to an operation object when you want to fetch, save, delete, and query the contents of the database. The database object tells the operation object where to get the data. (Calling the add(_:) method of the database assigns that database to the operation object implicitly.)

• Use a database object’s convenience methods to fetch, save, delete, and query the contents of the database directly. The convenience methods act on only one item at a time.

For operation objects that descend from the CKDatabaseOperation class, specify the database object to use when executing the operation.

• If you execute operations on your own custom queue, specify the database explicitly by assigning the appropriate CKDatabase object to the operation object’s database property.

• If you do not have your own queue, execute the operation object against a database implicitly by calling its add(_:) method.

The CKDatabase class offers convenience methods for accessing records, record zones, and subscriptions without an operation object. The convenience methods allow you to fetch, save, or delete a single item asynchronously and process the results on a background thread. There is also a convenience method to search for records in the database.