fileModificationDate
The date and time your app last modified the document file.
Declaration
var fileModificationDate: Date? { get set }Discussion
The modification date is updated by the open(completionHandler:), save(to:for:completionHandler:), and revert(toContentsOf:completionHandler:) methods. Its value is nil if none of these methods has completed successfully at least once. If you override any of these methods, you should be sure to set this property in your implementation.
UIKit sets this property before it calls the completion handlers of the open(completionHandler:), save(to:for:completionHandler:), and revert(toContentsOf:completionHandler:). If, outside of these methods or their completion handlers, you want to wait for any pending file operations to complete before you access this property, you can call performAsynchronousFileAccess(_:) and access the property value in the block parameter.