Embrace your Legacy... Code

Working with legacy code can be challenging and sometimes a little frustrating. In this talk, I would like to explore the positive side of it and how it can help to grow your skills and become a better developer.

Transcript

1. Embrace your Legacy... Code @tolkiana
2. ! Hello CodeMash! I'm Nelida @tolkiana Detroit Labs
3. Why do I care about Legacy code? @tolkiana
4. Photo by David Klein on Unsplash
5. I worked with a large legacy code base
6. What is Legacy Code? @tolkiana
7. Photo by Viktor Forgacs on Unsplash
8. The code that you wrote yesterday is Legacy Code -- Thom, former coworker @tolkiana
9. Photo by Clem Onojeghuo on Unsplash
10. Legacy code is not good or bad is just that, The Heritage that others have left for us to build upon @tolkiana
11. What legacy codebases taught me? @tolkiana
12. ! Patience @tolkiana
13. ! Persistence @tolkiana
14. ! Discipline @tolkiana
15. ! Curiosity @tolkiana
16. ❤ Empathy @tolkiana
17. ! Humility @tolkiana
18. Working with legacy code bases is fundamental for any software developer @tolkiana
19. Photo by Dane Deaner on Unsplash
20. What do I do now? @tolkiana
21. Legacy code takes a lot of time, care and love @tolkiana
22. ! 1. Understand @tolkiana
23. ✓ Read documentation if any @tolkiana
24. ✓ Read documentation if any ✓ Get to know your app as a user @tolkiana
25. ✓ Read documentation if any ✓ Get to know your app as a user ✓ Use the UI as an entry point @tolkiana
26. ✓ Read documentation if any ✓ Get to know your app as a user ✓ Use the UI as an entry point ✓ Pair @tolkiana
27. Working with legacy code is like surgery and doctors don’t operate alone. -- Michael C. Feathers @tolkiana
28. ✓ Read documentation if any ✓ Get to know your app as a user ✓ Use the UI as an entry point ✓ Pair ✓ Work on Bugs @tolkiana
30. ✏ 2. Document @tolkiana
31. ✓ Use it as a learning tool @tolkiana
32. ✓ Use it as a learning tool ✓ Use it to share knowledge @tolkiana
33. When teams aren’t aware of their architecture, it tends to degrade... The brutal truth is that architecture is too important to be left exclusively to a few people -- Michael C. Feathers @tolkiana
34. ✓ Use it as a learning tool ✓ Use it to share knowledge ✓ Use it to refresh your memory @tolkiana
35. But... When? Photo by Brianna Santellan on Unsplash
36. ! 3. Define a direction @tolkiana
37. Make your team the priority, without a healthy team, there's no code base that can be improved @tolkiana
38. ✅ 4. Test or improve current tests @tolkiana
39. Common testing traps @tolkiana
40. Common testing traps ✓ Letting unit tests to grow into mini integration tests @tolkiana
41. Common testing traps ✓ Letting unit test to grow into mini integration tests ✓ Wanting to test every single thing @tolkiana
42. Tests don’t have moral authority, they are there to document code -- Michael C. Feathers @tolkiana
43. ✂ 5. Break dependencies @tolkiana
44. class MyViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() let products = Order.shared.productsInCart() display(products) let mySetting = UserDefaults.standard.string(forKey: "mySetting") customize(mySetting) URLSession.shared.dataTask(with: URL(string: "http://service.com")!) { (data, response, error) in // do something } } } @tolkiana
45. class MyViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() let products = Order.shared.productsInCart() display(products) let mySetting = UserDefaults.standard.string(forKey: "mySetting") customize(mySetting) URLSession.shared.dataTask(with: URL(string: "http://service.com")!) { (data, response, error) in // do something } } } @tolkiana
46. class MyViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() let products = Order.shared.productsInCart() display(products) let mySetting = UserDefaults.standard.string(forKey: "mySetting") customize(mySetting) URLSession.shared.dataTask(with: URL(string: "http://service.com")!) { (data, response, error) in // do something } } } @tolkiana
47. class MyViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() let products = Order.shared.productsInCart() display(products) let mySetting = UserDefaults.standard.string(forKey: "mySetting") customize(mySetting) URLSession.shared.dataTask(with: URL(string: "http://service.com")!) { (data, response, error) in // do something } } } @tolkiana
48. class MyViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() let products = Order.shared.productsInCart() display(products) let mySetting = UserDefaults.standard.string(forKey: "mySetting") customize(mySetting) URLSession.shared.dataTask(with: URL(string: "http://service.com")!) { (data, response, error) in // do something } } } @tolkiana
49. class MyViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() let products = Order.shared.productsInCart() display(products) let mySetting = UserDefaults.standard.string(forKey: "mySetting") customize(mySetting) URLSession.shared.dataTask(with: URL(string: "http://service.com")!) { (data, response, error) in // do something } } } @tolkiana
50. class MyViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() let products = Order.shared.productsInCart() display(products) let mySetting = UserDefaults.standard.string(forKey: "mySetting") customize(mySetting) URLSession.shared.dataTask(with: URL(string: "http://service.com")!) { (data, response, error) in // do something } } } @tolkiana
51. // Stubbing to tests in Objective-C [order stub:@selector(productsInCart) andReturn:@[" "," "," "]]; [myController stub:@selector(order) andReturn:order]; [myController stub:@selector(urlSession) andReturn:mockSession]; [myController stub:@selector(userDefaults) andReturn:mockUserDefaults]; @tolkiana
52. // Stubbing to tests in Objective-C [order stub:@selector(productsInCart) andReturn:@[" "," "," "]]; [myController stub:@selector(order) andReturn:order]; [myController stub:@selector(urlSession) andReturn:mockSession]; [myController stub:@selector(userDefaults) andReturn:mockUserDefaults]; @tolkiana
53. // Stubbing to tests in Objective-C [order stub:@selector(productsInCart) andReturn:@[" "," "," "]]; [myController stub:@selector(order) andReturn:order]; [myController stub:@selector(urlSession) andReturn:mockSession]; [myController stub:@selector(userDefaults) andReturn:mockUserDefaults]; @tolkiana
54. class Order { static let shared = OrderManager() init(){} func productsInCart() -> [String] { var products: [String] = [] // Some complex and very scary code return products } func addProduct(_ product: String) { // Adding product } func removeProduct(_ product: String) { // Remove product } } @tolkiana
55. protocol OrderProtocol { func productsInCart() -> [String] } class Order: OrderProtocol { func productsInCart() -> [String] { var products: [String] = [] // Some complex and very scary code return products } } class FakeOrder: OrderProtocol { func productsInCart() -> [String] { return [" ! ", " " ", " # "] } } @tolkiana
56. protocol OrderProtocol { func productsInCart() -> [String] } class Order: OrderProtocol { func productsInCart() -> [String] { var products: [String] = [] // Some complex and very scary code return products } } class FakeOrder: OrderProtocol { func productsInCart() -> [String] { return [" ! ", " " ", " # "] } } @tolkiana
57. protocol OrderProtocol { func productsInCart() -> [String] } class Order: OrderProtocol { func productsInCart() -> [String] { var products: [String] = [] // Some complex and very scary code return products } } class FakeOrder: OrderProtocol { func productsInCart() -> [String] { return [" ! ", " " ", " # "] } } @tolkiana
58. class MyViewController: UIViewController { private let defaults: UserDefaults private let urlSession: URLSession private let order: OrderProtocol init(order: OrderProtocol, defaults: UserDefaults, urlSession: URLSession) { self.defaults = defaults self.urlSession = urlSession self.order = order super.init(nibName: nil, bundle: nil) } override func viewDidLoad() { super.viewDidLoad() let products = order.productsInCart() display(products) let mySetting = defaults.string(forKey: "mySetting") customize(mySetting) urlSession.dataTask(with: URL(string: "http://myService.com")!) { (data, response, error) in // do something } } } @tolkiana
59. class MyViewController: UIViewController { private let defaults: UserDefaults private let urlSession: URLSession private let order: OrderProtocol init(order: OrderProtocol, defaults: UserDefaults, urlSession: URLSession) { self.defaults = defaults self.urlSession = urlSession self.order = order super.init(nibName: nil, bundle: nil) } override func viewDidLoad() { super.viewDidLoad() let products = order.productsInCart() display(products) let mySetting = defaults.string(forKey: "mySetting") customize(mySetting) urlSession.dataTask(with: URL(string: "http://myService.com")!) { (data, response, error) in // do something } } } @tolkiana
60. class MyViewController: UIViewController { init(order: OrderProtocol = Order.shared, defaults: UserDefaults = .standard, urlSession: URLSession = .shared) { self.defaults = defaults self.urlSession = urlSession self.order = order super.init(nibName: nil, bundle: nil) } } // In production let controller = MyViewController() // In Tests let testController = MyViewController(orderManager: FakeOrder(), defaults: FakeDefaults(), urlSession: FakeSession()) @tolkiana
61. class MyViewController: UIViewController { init(order: OrderProtocol = Order.shared, defaults: UserDefaults = .standard, urlSession: URLSession = .shared) { self.defaults = defaults self.urlSession = urlSession self.order = order super.init(nibName: nil, bundle: nil) } } // In production let controller = MyViewController() // In Tests let testController = MyViewController(orderManager: FakeOrder(), defaults: FakeDefaults(), urlSession: FakeSession()) @tolkiana
62. class MyViewController: UIViewController { init(order: OrderProtocol = Order.shared, defaults: UserDefaults = .standard, urlSession: URLSession = .shared) { self.defaults = defaults self.urlSession = urlSession self.order = order super.init(nibName: nil, bundle: nil) } } // In production let controller = MyViewController() // In Tests let testController = MyViewController(orderManager: FakeOrder(), defaults: FakeDefaults(), urlSession: FakeSession()) @tolkiana
63. When we break dependencies, we can often write tests that can make more invasive changes safer. The trick is to do these initial refractories very conservatively. -- Michael C. Feathers @tolkiana
64. ! 6. Small, incremental improvements @tolkiana
65. Common refactoring traps @tolkiana
66. Common refactoring traps ✓ Getting over ambitious @tolkiana
67. Common refactoring traps ✓ Getting over ambitious ✓ Not setting a goal @tolkiana
68. Common refactoring traps ✓ Getting over ambitious ✓ Not setting a goal ✓ Not sharing our goal/architecture changes. @tolkiana
69. Working Effectively With Legacy Code Michael C. Feathers Refactoring Martin Fowler @tolkiana
70. Let others pride themselves about how many pages they have written, I'd rather boast about the ones I've read. -- Jorge Luis Borges @tolkiana
71. Thank you!! @tolkiana
72. Questions? Nelida Velázquez @tolkiana nelida.velazquez@detroitlabs.com