previousServerChangeToken
The token that identifies the starting point for retrieving changes.
Declaration
@NSCopying var previousServerChangeToken: CKServerChangeToken? { get set }Discussion
Each fetch request returns a unique token in addition to any changes. The token passes as a parameter to your fetchRecordChangesCompletionBlock handler. During a subsequent fetch request, providing the previous token causes the server to return only the changes that occur after the previous fetch request. Tokens are opaque data objects that you can write to disk safely and reuse later.
Typically, you set the value of this property when you initialize the operation object. If you intend to change the record zone, update the value of the property before executing the operation or submitting it to a queue.