While Your App is Sleeping

Transcript

1. While Your App Was Sleeping Gwendolyn Weston
 @purpleyay
2. Background Transfer Services allows uploading or downloading requests to continue on after app is terminated
3. Motivation
4. A Teakettle • That requires you to stand near it • As well as continue to watch in order for it to boil water
5. Where can this happen in our apps?
6. PlanGrid
7. To guarantee download completion • Users would have to change their settings so that the device never locks • Stay on the app
8. Downloading without Background Transfer Services is like watching water boil.
9. Overview • How to download in the foreground • How to make that request background compatible • How to navigate common pitfalls
10. Downloading in the foreground
11. Downloading in Foreground
12. Downloading in Foreground NSURLSession: vends and manages requests
13. Downloading in Foreground sharedSession: singleton session with default settings
14. Downloading in Foreground NSURLSessionDownloadTask: the request
15. NSURLSessionTask • NSURLSessionDownloadTask • NSURLSessionUploadTask • NSURLSessionDataTask - short-lived requests (not background compatible!)
16. We get tasks by feeding our session URLs
17. Cookie Monster as NSURLSession
19. Downloading in Foreground
20. Downloading in Foreground
21. Downloading in Foreground
22. Downloading in Foreground
23. Downloading in the background
24. Downloading in Foreground
26. NSURLSessionConfiguration: defines request behaviour and policies
28. Identifiers must be unique!
29. “I’m done downloading!!! Wake up!” application: handleEventsForBackgroundURLSession: completionHandler “It’s me, the session called waterBoiling Session!”
31. !!Must!! re-instantiate session with identifier or delegate methods for request will not get called.
32. “The behavior of multiple sessions sharing the same identifier is undefined.”
33. Downloading in Background
35. Downloading in Background
36. “Completion handler blocks are not supported in background sessions”
37. Pitfall no completion handlers
38. Downloading in Background
39. “I’m done downloading!!! Wake up!” URLSession:downloadTask:didFinishDownloadingTo URL: “It’s me, the request for task 42 in the session called boilingWaterSession!”
40. The delegate!
41. Downloading in Background
43. Downloading in Background
44. Pitfall No auxiliary request info
45. Promising… ?
46. Nope.
47. Subclasses?
49. Downloading in Background
50. “Can I have—“ “No.” “Just one subclass—“ “No.” NSURLSession
51. Persistence!
52. Downloading in Background
53. YUSS.
54. Questions? @purpleyay