Lost in maintenance in Swift

How to support unsupportable :)

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