"Lost in maintenance: criteria of maintainable in Swift" by Paul Taykalo

We rarely start projects from scratch and often blame our predecessors for their code. Problems begin yet upon estimation of live project’s maintainability. In his talk Taykalo Paul, iOS Team Leader at Stanfy, will reveal some particular criteria to consider on existing codebases’ maintainability.
He’ll also share his experience communicating current project’s state and related risks to stakeholders. Paul will show some practical decisions that will help to leave the project in better state than it was previously. Refactoring techniques, unit tests’ coverage, CoreData migrations are here to help.

This talk was made for CocoaHeads Kyiv #12 which took place July 22 2017.

Transcript

1. Lost in maintenance: criteria of maintainable in Swift by Paul Taykalo, Stanfy Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 1
2. Plan » Derermining project maintainability » Maintaining unmaintainable » Rewriting? » Speaking about maintainability Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 2
3. We've got a project to check Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 3
4. How we check project status Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 4
5. How should we check project status Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 5
6. How should we check project status Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 6
7. Be objective in your decisions Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 7
8. Where does this list came from? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 8
9. We've got a project to check Be objective Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 9
10. Everything is analyzed and checked What's next? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 10
11. We decided not to take the project Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 11
12. The end Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 12
13. Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 13
14. So, you've got a project Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 14
15. So, you've got a project First steps Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 15
16. Knowledge sharing Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 16
17. Are there any tests? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 17
18. Are there any tests? You know the answer :( Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 18
19. Are there any tests? You know the answer :( Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 19
20. Documentation Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 20
21. Documentation Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 21
22. Documentation Hack How to read documentation Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 22
23. U is for Understading Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 23
24. How to deal with Legacy Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 24
25. Rules Boyscout Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 25
26. One (two) thing at the time Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 26
27. Remove Dead Code Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 27
28. Aim Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 28
29. Rewrite! Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 29
30. Rewrite? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 30
31. Few More things before Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 31
32. Semantic Meaning Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 32
33. Semantic Meaning if item.row == 2 { ... } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 33
34. Semantic Meaning if item.row == 2 { ... } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 34
35. Semantic Meaning if api.version > 2 { ... } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 35
36. Semantic Meaning if api.version > 2 { ... } let supportsThrottling = api.version > 2 if supportsThrottling { ... } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 36
37. Semantic Meaning if api.version > 2 { ... } extension Api { var supportsThrottling: Bool { return version > 2} } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 37
38. Semantic Meaning if let object = notification.object as? UIViewController , object == self { ... } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 38
39. Semantic Meaning if let object = notification.object as? UIViewController , object == self { ... } let notificationWasSentByUs = notification.object == self if notificationWasSentByUs { ... } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 39
40. Semantic Meaning if let currentUser = User.currentUser(inContext: mainContext) , currentUser.username != nil && currentUser.apiToken != nil ... else if let currentUser = User.currentUser(inContext: mainContext) , currentUser.username == nil && currentUser.apiToken != nil ... else Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 40
41. Semantic meaning let user = User.currentUser(inContext: self.appData.mainContext) let userHasValidUserName = user?.username != nil let userHasValidToken = user?.apiToken != nil Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 41
42. Semantic meaning if userHasValidToken && userHasValidUserName ... else if userHasValidToken && userHasNoName ... else Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 42
43. Do it on daily basis Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 43
44. Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 44
45. Always be careful with any changes Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 45
46. Always be careful with any changes func overloaded(value: Double) -> String { return "Double" } func overloaded(value: Any) -> String { return "Any" } let size: Double? = dictionary["size"] let value = size ?? 0.0 let complex = overloaded(size ?? 0.0) // Any let simple = overloaded(value) // Double Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 46
47. What else can we do? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 47
48. What are these functions about? UIImage -> UIImage String -> String -> String URL -> UIImage Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 48
49. Phantom types Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 49
50. Phantom types PhotoAlbumImage -> TumbnailImage UserID -> AddressID -> Address FileURL -> ThumbnailImage Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 50
51. Phantom types struct FilteredImage { // this will be filtered only let image: UIImage } struct BigImage { // in memory image private(set) var inMemoryImage: UIImage? // stored private var storedURL: URL? var image: UIImage { // return from the memory // or load from the fs } } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 51
52. Phantom types struct FileSystemURL { let url: NSURL // Failable initializer init?(url: NSURL) } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 52
53. Phantom types reasoning Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 53
54. Phantom types » Concrete » Unique behaviour » Control Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 54
55. Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 55
56. What else can we do? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 56
57. Hell? vs Hell! Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 57
58. Hell? vs Hell! ! Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 58
59. Hell? vs Hell! ? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 59
60. Hell? vs Hell! struct User { let name: String? let token: String? } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 60
61. Hell? vs Hell! struct UnverifiedUser {} struct User { let name: String } struct LoggedUser { let user: User let token: String // TokenString } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 61
62. Hell? vs Hell! // First var itemsPerKey: [Key: Item] = [:] // Then var itemsPerKey: [Key: Item] = [:] var isDeleted: [Key: Bool] = [:] Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 62
63. Hell? vs Hell! enum ItemState { case assigned(let item) case deleted var item: Item? { if .assigned(let item) = self { return item } return nil } } var itemsPerKey: [Key: ItemState] = [:] Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 63
64. Hell? vs Hell! enum UploadingState { case notStarted case uploading(Foundation.Operation) case uploaded case failed(Error) func operation() -> Foundation.Operation? { switch self { case .uploading(let op): return op default: return nil } } func isUploading() -> Bool { if case .uploading = self { return true } return false } } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 64
65. Hell? vs Hell! public enum Result<Value, Error: Swift.Error> { case success(Value) case error(Error) } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 65
66. Results and costs Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 66
67. Rewrite all the things! Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 67
68. How to make changes in the project Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 68
69. How to make changes in the project Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 69
70. How to make changes in the project » What is going on? » Freeze current behaviour » Write down desired behaviour » Check » Make sure that all unrelated sidefects still there Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 70
71. How to make changes in the project » Make tests on current behavor » Make change » Check Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 71
72. Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 72
73. But I cannot test it because... » I dont understand how class works » I cannot instantiate class in test env » I cannot test method - it's too bit » I cannot... Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 73
74. . . It's too big for testing Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 74
75. 'But I cannot' solutions » Test method in class » Make an helper and use it class Huge { func perform { if object.price as? String == } } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 75
76. 'But I cannot' solutions class Huge { func perform { if let price = object.price as? String } } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 76
77. 'But I cannot' solutions struct Price { init?(object: [String: Any]) {} var priceToShow: String {} var discont: String {} } Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 77
78. 'But I cannot' solutions protocol Dispatcher { func background(_ block: @escaping (() -> Void)) func main(_ block: @escaping (() -> Void)) func main_from_background(_ block: @escaping(() -> Void)) func background_delay(_ delay: Int64, block: @escaping (() -> Void)) func main_delay(_ delay: Int64, block: @escaping (() -> Void)) } // for everything else class DefaultDispatcher: Dispatcher {} // For tests class SyncDispatcher: Dispatcher {} Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 78
79. 'But I cannot' solutions » Core Data » Views » Snaphots » Hardware? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 79
80. This is ... Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 80
81. This is legacy! Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 81
82. L - is for Logs Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 82
83. M - is for Measurements Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 83
84. N - is for "No hope without Logs and Measurements" Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 84
85. Now you are allowed to rewrite something Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 85
86. Small history about scrolling Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 86
87. Small history about scrolling » App is not using cache Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 87
88. Small history about scrolling » ✅ Not using cache » ❌ Freezing Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 88
89. Small history about scrolling » ✅ Not using cache » ✅ Freezing (disk cacke) » ❌ Freezing ( after MW) Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 89
90. Small history about scrolling » ✅ Not using cache » ✅ Freezing (disk cacke) » ✅ Freezing ( after MW) » ❌ Lags (Jpeg Decoding) Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 90
91. Small history about scrolling » ✅ Not using cache » ✅ Freezing (disk cacke) » ✅ Freezing ( after MW) » ✅ Lags (Jpeg Decoding) » ❌ Out of memory crashes Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 91
92. Small history about scrolling » ✅ Not using cache » ✅ Freezing (disk cacke) » ✅ Freezing ( after MW) » ✅ Lags (Jpeg Decoding) » ❌ Out of memory crashes » ??????? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 92
93. There's a library for that Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 93
94. There's a library for that ios-twitter-image- pipeline Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 94
95. Wanna try something bigger? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 95
96. Rewriting Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 96
97. Rewriting » Modularity » Testing! » Enclosing » Unification Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 97
98. Modularity What if I tell you that there can be more than one storyboard? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 98
99. Testing Start writing tests :( - There's no time for it - I cannot sell it to the customer - I am supporting a legacy application without unit tests. - QA and User Acceptance Testing is far more effective in finding bugs - I don’t know how to unit test, or I don’t know how to write good unit tests Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 99
100. Testing There'll be no failed tests if there's no tests Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 100
101. Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 101
102. Working with Product Owner Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 102
103. Working with Product Owner Selling and tradeoffs Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 103
104. Working with Product Owner Are you better? Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 104
105. Working with Product Owner Facts Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 105
106. Recap Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 106
107. Thank you Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 107
108. Lost in maintenance by Paul Taykalo, Stanfy @TT_Kilew Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 108
109. The end Lost in maintenance, by Paul Taykalo, #cocoaheadskyiv 109