MVVM, VIPER, MVC are quite different approaches to architecturing mobile applications. But they are based on several fundamental principles, like SOLID. Whatever architectural pattern you choose to use following these simple principles will help you write clean and maintainable code. It's best to learn from mistakes. We are going to talk about each SOLID principle in the following way: "Violation of principle -> Discussion -> Refactoring". After this talk the audience should clearly understand how to apply SOLID principles to typical iOS development problems.

1. Кто подставил
Барбару Лисков?
или Кто кого SOLID?
Сергей Крапивенский, Rambler&Co

2. как сказал наш великий полководец Суворов
“Do Not Learn Frameworks”

3. Фундаментальные знания

4. Фундаментальные знания
Язык

5. Фундаментальные знания
Язык
Фреймворки

6. Фундаментальные знания
Язык
Фреймворки

7. RayWenderlich - driven development
Senior ReactiveCocoa Developer
Рамблер - секта VIPER

8. Фундаментальные знания
Язык
Фреймворки

9. Фундаментальные знания
Язык
Фреймворки

10. Фундаментальные знания
Язык
Фреймворки

11. Фундаментальные знания
• Структуры данных
• Алгоритмы
• Паттерны
• DRY, KISS, YAGNI
• SOLID
• И многое другое

13. Single responsibility principle
Open-closed principle
Liskov substitution principle
Interface segregation principle
Dependency inversion principle

14. Single Responsibility Principle
“A class should have only one
reason to change”

15. MassiveViewController
1.Ответственности сильно связаны
2.Класс перестает помещаться в голове
3.Тяжело поддерживать и тестировать

16. UITableViewController
1.Изменение логики работы с таблицей
2.Поменять иерархию вьюшек

17. UITableViewController
Решение проблемы: не использовать его

18. Запуск приложения
Push Notifications
Quick Actions
Уведомления о
состояниях приложения
Открытие по URL
Фоновая
загрузка данных
AppDelegate

19. AppDelegate
Запуск приложения Quick Actions
ПоискPush Notifications
Открытие URL
Состояния
приложения
Загрузка в фоне
Handoff
Extensions

20. AppDelegate
Запуск приложения Quick Actions
ПоискPush Notifications
Открытие URL
Состояния
приложения
Загрузка в фоне
Handoff
Extensions
https://github.com/rambler-digital-solutions/RamblerAppDelegateProxy

21. SRP о снижении сложности

22. Single responsibility principle
Open-closed principle
Liskov substitution principle
Interface segregation principle
Dependency inversion principle

23. Open-Closed Principle
“Software entities (classes,
modules, functions, etc.) should
be open for extension, but closed
for modification”

24. Простой и устойчивый
дизайн

25. Новость
Новость
Новость
Новость

26. Новость
Новость
Новость
Новость
Новость с фото
Новость с фото

27. Новость
Новость
Новость
Новость
Новость с фото
Новость с фото
Реклама
Реклама

28. } else ...
return cell;
}
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeue...];
id model = [self modelAtIndex:indexPath.row];
if ([model isKindOfClass:[News class]]) {
NewsCell *newsCell = (NewsCell *)cell;
[newsCell setupWithNews:model];
} else if ([model isKindOfClass:[Advertisement class]]) {
AdvertisementCell *adCell = (AdvertisementCell *)cell;
[adCell setupWithAd:model];

29. } else ...
return cell;
}
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeue...];
id model = [self modelAtIndex:indexPath.row];
if ([model isKindOfClass:[News class]]) {
NewsCell *newsCell = (NewsCell *)cell;
[newsCell setupWithNews:model];
} else if ([model isKindOfClass:[Advertisement class]]) {
AdvertisementCell *adCell = (AdvertisementCell *)cell;
[adCell setupWithAd:model];

30. } else ...
return cell;
}
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeue...];
id model = [self modelAtIndex:indexPath.row];
if ([model isKindOfClass:[News class]]) {
NewsCell *newsCell = (NewsCell *)cell;
[newsCell setupWithNews:model];
} else if ([model isKindOfClass:[Advertisement class]]) {
AdvertisementCell *adCell = (AdvertisementCell *)cell;
[adCell setupWithAd:model];

31. } else ...
return cell;
}
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeue...];
id model = [self modelAtIndex:indexPath.row];
if ([model isKindOfClass:[News class]]) {
NewsCell *newsCell = (NewsCell *)cell;
[newsCell setupWithNews:model];
} else if ([model isKindOfClass:[Advertisement class]]) {
AdvertisementCell *adCell = (AdvertisementCell *)cell;
[adCell setupWithAd:model];

32. } else ...
return cell;
}
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeue...];
id model = [self modelAtIndex:indexPath.row];
if ([model isKindOfClass:[News class]]) {
NewsCell *newsCell = (NewsCell *)cell;
[newsCell setupWithNews:model];
} else if ([model isKindOfClass:[Advertisement class]]) {
AdvertisementCell *adCell = (AdvertisementCell *)cell;
[adCell setupWithAd:model];

34. - (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
id model = [self modelAtIndex:indexPath.row];
UITableViewCell<ConfigurableCell> *cell = ...;
[cell configureWithObject:model];
return cell;
}

35. NewsCell PhotoCell AdCell
<ConfigurableCell>
- (void)configure:(<CellObject>)object;
News Photo Advert
<CellObject>
- (Class)cellClass;

36. Когда применять?

38. Single responsibility principle
Open-closed principle
Liskov substitution principle
Interface segregation principle
Dependency inversion principle

40. Liskov Substitution Principle
“Subtypes must be substitutable
for their base types”

41. Нужен для проверки
корректности наследования

42. - (void)hideViews {
[UIView animateWithDuration:1.0
animations:^
{
for (UIView *view in self.animatableViews) {
view.alpha = 0.5f;
}
}];
}

43. UIView
UIVisualEffectView
Всё ок !
<UIVisualEffectView> is being asked to animate its
opacity. This will cause the effect to appear broken until
opacity returns to 1

44. ¯_( )_/¯

45. Single responsibility principle
Open-closed principle
Liskov substitution principle
Interface segregation principle
Dependency inversion principle

46. Interface Segregation Principle
“Clients should not be forced to
depend on methods that they
do not use”

47. MailAPIClient
- auth
- findContact
- getMailboxes
- createMailbox
- sendMail
Auth Contacts Mailboxes Messages
- auth
- findContact
- getMailboxes
- createMailbox
- sendMail
- auth
- findContact
- getMailboxes
- createMailbox
- sendMail
- auth
- findContact
- getMailboxes
- createMailbox
- sendMail
- auth
- findContact
- getMailboxes
- createMailbox
- sendMail

48. AuthServiceMailboxServiceContactServiceMessageService
Auth Contacts Mailboxes Messages
- auth
- findContact
- getMailboxes
- createMailbox
- sendMail
- auth
- findContact
- getMailboxes
- createMailbox
- sendMail
- auth
- findContact
- getMailboxes
- createMailbox
- sendMail
- auth
- findContact
- getMailboxes
- createMailbox
- sendMail
MailAPIClient

49. ISP - это не SRP

50. - sendSelfDestructMessage
- deleteBothMessages
ChatChannel
- loadMessages
- sendMessage
- replyToMessage
- forwardMessage
ChannelSecretChat Supergroup
- banUser
Group
- loadMessages
- sendMessage
- replyToMessage
- forwardMessage
- sendSelfDestruct
- deleteBoth
- pinMessage
- banUser
- pinMessage - loadMessages
- sendMessage
- replyToMessage
- forwardMessage
- sendSelfDestruct
- deleteBoth
- pinMessage
- banUser
- loadMessages
- sendMessage
- replyToMessage
- forwardMessage
- sendSelfDestruct
- deleteBoth
- pinMessage
- banUser
- loadMessages
- sendMessage
- replyToMessage
- forwardMessage
- sendSelfDestruct
- deleteBoth
- pinMessage
- banUser

51. Single responsibility principle
Open-closed principle
Liskov substitution principle
Interface segregation principle
Dependency inversion principle

52. Dependency Inversion Principle
“A. High-level modules should not
depend on low-level modules.
Both should depend on
abstractions”

53. Dependency Inversion Principle
“B. Abstractions should not
depend on details. Details should
depend on abstractions”

54. - (void)displayNews {
NSPredicate *newsPredicate = ...;
NSArray *news = [News MR_findAllWithPredicate:newsPredicate];
// Отображаем новости
}
Зависимость от Core Data

55. NewsViewController MagicalRecord
Realm😓

56. @protocol NewsProvider <NSObject>
- (NSArray *)obtainNewsForDate:(NSDate *)date;
@end
Зависимость от Core Data
- (void)displayNews {
NSDate *todayDate = ...;
NSArray *news = [self.newsProvider obtainNewsForDate:todayDate];
// Отображаем новости
}

57. @protocol NewsProvider <NSObject>
- (NSArray *)obtainNewsForDate:(NSDate *)date;
@end
Зависимость от Core Data
- (void)displayNews {
NSDate *todayDate = ...;
NSArray *news = [self.newsProvider obtainNewsForDate:todayDate];
// Отображаем новости
}

58. @interface NewsViewController : UIViewController
- (instancetype)initWithNewsProvider:(id<NewsProvider>)newsProvider;
@end
Зависимость от Core Data

59. NewsViewController <NewsProvider>
MagicalRecord
NewsProvider

60. Зависимости инвертированы #

61. Серебряной пули нет 😢

62. - Оноре де Бальзак
“Обстоятельства переменчивы,
принципы - никогда”