The fields to retrieve for the requested records.
- iOS 8.0+
- macOS 10.10+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 3.0+
Use this property to limit the amount of data retrieved for each record during the search operation. The value is an array of
NSString objects, each of which contains the name of a field from the target records. When you retrieve a given record, only fields whose names match one of the specified keys are included in the returned record. If you specify
nil, the operation retrieves all keys for the record. The default value of this property is
If you intend to specify a value, you must do so before executing the operation or submitting the operation object to a queue.