Apple provides a mechanism for updating a Pass that has been added to Passbook by a user. This process involves sending a push notification to the user's device, and implementing a REST API that will respond to the device's requests and provide the relevant updated Pass information.
The first stage in updating a Pass is to send a Push Notification to the user's device to prompt the Pass update process. The process for sending Apple Push Notifications (APNs) is outside the scope for this book, and the assumption will made that the facility to send the appropriate APN is available. Further information on APNs can be found in Apple's documentation: