Debugging - Things your senior hasn't told you about

We as developers are spending 50% of our time either fixing bugs or making code work. In this talk we’re going over breakpoints, commands, arguments and tools that will help you be more efficient and faster when debugging your Apps.

Transcript

1. DEBUGGING Things your Senior hasn't told you about (yet) 1 — @_Caro_N, 4/16/2018
2. 2 — @_Caro_N, 4/16/2018
3. WHAT PROBLEMS DO WE FACE? 3 — @_Caro_N, 4/16/2018
4. WE DON'T HAVE ENOUGH INFORMATION 4 — @_Caro_N, 4/16/2018
5. TIME CONSUMING TASKS 5 — @_Caro_N, 4/16/2018
6. WE DON'T KNOW ABOUT GOOD PRACTICES 6 — @_Caro_N, 4/16/2018
7. COVERED TOPICS ▸ Get more information 7 — @_Caro_N, 4/16/2018
8. COVERED TOPICS ▸ Get more information ▸ How you can speed up debugging 8 — @_Caro_N, 4/16/2018
9. COVERED TOPICS ▸ Get more information ▸ How you can speed up debugging ▸ Best practices for error handling & debugging 9 — @_Caro_N, 4/16/2018
10. 1. UNRESPONSIVE TO SCROLLS AND CLICK 10 — @_Caro_N, 4/16/2018
11. 2. HIGH MEMORY PRESSURE 11 — @_Caro_N, 4/16/2018
12. 3. STUCK IN UIKIT 12 — @_Caro_N, 4/16/2018
13. 13 — @_Caro_N, 4/16/2018
14. LLDB TO THE RESCUE! 14 — @_Caro_N, 4/16/2018
15. GENERAL PURPOSE REGISTERS: 15 — @_Caro_N, 4/16/2018
16. 16 — @_Caro_N, 4/16/2018
17. 17 — @_Caro_N, 4/16/2018
18. LAUNCH ARGUMENTS 18 — @_Caro_N, 4/16/2018
19. 19 — @_Caro_N, 4/16/2018
20. 20 — @_Caro_N, 4/16/2018
21. 21 — @_Caro_N, 4/16/2018
22. ▸ UIViewLayoutDebugger ▸ ConcurrencyDebug ▸ Migrationdebug & SQLDebug ▸ NSTraceEvents 22 — @_Caro_N, 4/16/2018
23. What's New in Auto Layout https://developer.apple.com/videos/play/wwdc2016/236 23 — @_Caro_N, 4/16/2018
24. LAUNCH ARGUMENTS -com.apple.CoreData.ConcurrencyDebug 1 Core Data Concurrency Debugging by Ole Begemann https://oleb.net/blog/2014/06/core-data-concurrency-debugging/ 24 — @_Caro_N, 4/16/2018
25. LAUNCH ARGUMENTS -com.apple.CoreData.MigrationDebug 1 -com.apple.CoreData.SQLDebug 3 25 — @_Caro_N, 4/16/2018
26. LAUNCH ARGUMENTS /Applications/TextEdit.app/Contents/MacOS/TextEdit -NSTraceEvents YES 26 — @_Caro_N, 4/16/2018
27. ✨ iOS Debugging Magic https://developer.apple.com/library/content/technotes/tn2239 ✨ Mac OS X Debugging Magic https://developer.apple.com/library/content/technotes/tn2124 27 — @_Caro_N, 4/16/2018
28. SPEED UP DEBUGGING 28 — @_Caro_N, 4/16/2018
29. KEYPATHS let colorObservation = textFieldBackground.observe(\.backgroundColor, options:[.old, .new]) { (_, change) in) log.debug("color:\( change.oldValue ) -> \( change.newValue )") log.debug("") } 29 — @_Caro_N, 4/16/2018
30. (lldb) po UIApplication.shared error: property 'shared' not found on object of type 'UIApplication' 30 — @_Caro_N, 4/16/2018
31. (lldb) po UIApplication.shared error: property 'shared' not found on object of type 'UIApplication' (lldb) expr -l swift -O -- UIApplication.shared <UIApplication:0x7fa384d00260> 31 — @_Caro_N, 4/16/2018
32. (lldb) po UIApplication.shared error: property 'shared' not found on object of type 'UIApplication' (lldb) expr -l swift -O -- UIApplication.shared <UIApplication:0x7fa384d00260> (lldb) expr @import UIKit (lldb) expr @import Foundation 32 — @_Caro_N, 4/16/2018
33. 33 — @_Caro_N, 4/16/2018
34. USEFUL BREAKPOINTS -NSKVODeallocateBreak 34 — @_Caro_N, 4/16/2018
35. USEFUL BREAKPOINTS -Exception Breakpoint: Objective-C Debugger command: po $arg1 35 — @_Caro_N, 4/16/2018
36. USEFUL BREAKPOINTS -UIApplicationMain Debugger command: expr @import UIKit Debugger command: expr @import Foundation -NSKVODeallocateBreak -Exception Breakpoint: Objective-C Debugger command: po $arg1 User Breakpoints in Xcode by Michael Ochs https://pspdfkit.com/blog/2017/user-breakpoints-in-xcode/ 36 — @_Caro_N, 4/16/2018
37. GOOD PRACTICES FOR ERROR HANDLING 37 — @_Caro_N, 4/16/2018
38. ASSERTIONS ▸ assert() ▸ assertionFailure() 38 — @_Caro_N, 4/16/2018
39. ASSERT func transformString(string: String?) -> String { assert(string != nil, "Invalid parameter") return string! + "_transforme" } 39 — @_Caro_N, 4/16/2018
40. ASSERTIONFAILURE case RemoteNetworkCell.cloud.rawValue: if let networkCell = tableView.dequeueReusableCell(withIdentifier: VLCRemoteNetworkCell.cellIdentifier) { networkCell.textLabel?.text = cloudVC.title networkCell.detailTextLabel?.text = cloudVC.detailText networkCell.imageView?.image = cloudVC.cellImage return networkCell } case RemoteNetworkCell.wifi.rawValue: if let wifiCell = tableView.dequeueReusableCell(withIdentifier: VLCWiFiUploadTableViewCell.cellIdentifier()) { return wifiCell } default: assertionFailure("We're not handling a new CellType, add him to the cases") } assertionFailure("Cell is nil, did you forget to register the identifier?") return UITableViewCell() 40 — @_Caro_N, 4/16/2018
41. SWIFT_OPTIMIZATION_LEVEL = -Onone // debug SWIFT_OPTIMIZATION_LEVEL = -O // release SWIFT_OPTIMIZATION_LEVEL = -Ounchecked // unchecked release 41 — @_Caro_N, 4/16/2018
42. PRECONDITION & FATALERROR ▸ precondition() ▸ preconditionFailure() ▸ fatalError() 42 — @_Caro_N, 4/16/2018
43. PRECONDITION internal init(_repeating repeatedValue: Element, count: Int) { _precondition(count >= 0, "Repetition count should be non-negative") self.count = count self.repeatedValue = repeatedValue } 43 — @_Caro_N, 4/16/2018
44. FATALERROR internal enum _Normalization { // ICU's NFC unorm2 instance internal static var _nfcNormalizer: OpaquePointer = { var err = __swift_stdlib_U_ZERO_ERROR let normalizer = __swift_stdlib_unorm2_getNFCInstance(&err) guard err.isSuccess else { // This shouldn't be possible unless some deep (unrecoverable) system // invariants are violated fatalError("Unable to talk to ICU") } return normalizer }() 44 — @_Caro_N, 4/16/2018
45. DEBUG RELEASE RELEASE function -Onone -O -Ounchecked assert() Yes No No assertfailure() Yes No No precondition() Yes Yes No preconditionFailu re() Yes Yes Yes fatalerror() Yes Yes Yes 45 — @_Caro_N, 4/16/2018
46. SUMMARY ▸ Read register, Launch arguments ▸ Keypaths, User Breakpoints ▸ assert, precondition, fatalerror 46 — @_Caro_N, 4/16/2018
47. Resources: Launch Arguments & Environment Variables by Mattt Thompson http://nshipster.com/launch-arguments-and-environment-variables/ Swift Assertions by Andy Bargh https://andybargh.com/swift-assertions/ Swift asserts - the missing manual by Marcin Krzyzanowski http://blog.krzyzanowskim.com/2015/03/09/swift-asserts-the-missing-manual/ Debugging by Paul Hudson https://www.hackingwithswift.com/read/18/overview 47 — @_Caro_N, 4/16/2018
48. THANKS 48 — @_Caro_N, 4/16/2018