21. Push Notifications
When Web services need to communicate directly with users, push notifications provide a powerful solution. They deliver messages directly to the device screen via a special Apple service. Push notifications lets devices display an alert, play a custom sound, or update an application badge. In this way, off-device services connect with an iOS-based client, letting them know about new data or updates. Unlike most other iOS development arenas, nearly all the push story takes place off the device. Developers must create Web-based services to manage and deploy these updates. In this chapter, you learn how push notifications work and dive into the details needed to create your own push-based system.