Programming iOS 9

Part IV. Final Topics

This part of the book is a miscellany of topics.

• Chapter 23 is about files. It explains how your app can store data on disk to be retrieved the next time the app runs (including both standalone files and user defaults). It also discusses sharing files with the user through iTunes and with other apps, plus the document architecture and iCloud, and concludes with a survey of how iOS can work with some common file formats (XML, SQLite, Core Data, and image files).
• Chapter 24 introduces networking, with an emphasis on HTTP downloading of data. It also introduces some specialized forms of networking such as on-demand resources and in-app purchasing.
• Chapter 25 is about threads. Making your code multithreaded can introduce great complexity and is not a beginner topic, but you still might need to understand the basic concepts of multithreading, either in order to prevent a lengthy task from blocking user interaction with your app, or because some framework explicitly relies on it. Particular attention is paid to the advantages of NSOperation and Grand Central Dispatch.
• Chapter 26 describes how iOS supports undo in your app.