![[go back];](https://image.slidesharecdn.com/adoptingswiftgenerics-160716090009/85/Adopting-Swift-Generics-11-320.jpg)
![Typical api request
API Resource
/users
Raw Data
NSData?
Parsed Object
[String: String]?
Model
User?
Request Parsing
ObjectMapper
12](https://image.slidesharecdn.com/adoptingswiftgenerics-160716090009/85/Adopting-Swift-Generics-12-320.jpg)
![Implementation
@implementation DataProvider
- (void)fetch:(NSString *)resources
mappingClass:(Class)mappingClass
completion:(void(^)(NSArray<id<Mappable>> *results))completion {
// Load data...
// Parse data...
if ([mappingClass conformsToProtocol:@protocol(Mappable)]) {
id result = [mappingClass initWithDictionary:response];
completion(@[result]);
}
}
@end
13](https://image.slidesharecdn.com/adoptingswiftgenerics-160716090009/85/Adopting-Swift-Generics-13-320.jpg)
![The problem?
@implementation DataProvider
- (void)fetch:(NSString *)resources
mappingClass:(Class)mappingClass
completion:(void(^)(NSArray<id<Mappable>> *results))completion {
// Load data...
// Parse data...
if ([mappingClass conformsToProtocol:@protocol(Mappable)]) {
id result = [mappingClass initWithDictionary:response];
completion(@[result]);
}
}
@end
14](https://image.slidesharecdn.com/adoptingswiftgenerics-160716090009/85/Adopting-Swift-Generics-14-320.jpg)
![What run time means?
DataProvider *provider = [DataProvider new];
[provider fetch:@"/users"
mappingClass:[NSString class] // compiler doesn’t warn you here...
completion:^(NSArray<User *> *results) {
}];
16](https://image.slidesharecdn.com/adoptingswiftgenerics-160716090009/85/Adopting-Swift-Generics-16-320.jpg)
![You are doing it wrong with Swift
let dataProvider = DataProvider()
dataProvider.fetch("/resource", mappingClass: User.self) { result in
// code smell...
guard let users = result.values as? [User] else {
return
}
}
17](https://image.slidesharecdn.com/adoptingswiftgenerics-160716090009/85/Adopting-Swift-Generics-17-320.jpg)
![TableKit
import TableKit
let clickAction = TableRowAction<String, MyTableViewCell>(.click) { (data) in
}
let row = TableRow<String, MyTableViewCell>(item: "string", actions: [clickAction])
tableDirector += TableSection(rows: [row])
31](https://image.slidesharecdn.com/adoptingswiftgenerics-160716090009/85/Adopting-Swift-Generics-31-320.jpg)
![The power of declarative approach
let rows: [Row] = strings.map { TableRow<String, MyTableViewCell>(item: $0) }](https://image.slidesharecdn.com/adoptingswiftgenerics-160716090009/85/Adopting-Swift-Generics-33-320.jpg)
![The view layer is simply
a mapping of our data layer
let rows: [Row] = users
.filter({ $0.active })
.map({ UserViewModel(user: $0) })
.map({ TableRow<UserViewModel, UserTableViewCell>(item: $0) })](https://image.slidesharecdn.com/adoptingswiftgenerics-160716090009/85/Adopting-Swift-Generics-34-320.jpg)
Adopting Swift Generics
- 1. Adopting Swift Generics Перейдем на <T> Max Sokolov - iOS dev @ Avito masokolov@avito.ru max_sokolov
- 2. 2
- 3. 3 World’s 3rd Biggest Classifieds Site 35m users per month 500k items per day 100k deals
- 4. Agenda • Dynamic type-casting problem • Generics in Swift • Protocols with associated types • Declarative type-safe UIKit • Livecoding! 4
- 5. 🤔 class Matrix<T: Choiceable where T.T == T, T: Learnable, T: Fateable>
- 6. Generic code enables you to write flexible, reusable functions and types that can work with any type, subject to requirements that you define. You can write code that avoids duplication and expresses its intent in a clear, abstracted manner. Apple docs What for? 6
- 7. 😎
- 10. Why? • One team of 5 people • 3 different apps with shared components (mostly Swift) • 20 private CocoaPods • Large code base (~100k) 10
- 11. [go back];
- 12. Typical api request API Resource /users Raw Data NSData? Parsed Object [String: String]? Model User? Request Parsing ObjectMapper 12
- 13. Implementation @implementation DataProvider - (void)fetch:(NSString *)resources mappingClass:(Class)mappingClass completion:(void(^)(NSArray<id<Mappable>> *results))completion { // Load data... // Parse data... if ([mappingClass conformsToProtocol:@protocol(Mappable)]) { id result = [mappingClass initWithDictionary:response]; completion(@[result]); } } @end 13
- 14. The problem? @implementation DataProvider - (void)fetch:(NSString *)resources mappingClass:(Class)mappingClass completion:(void(^)(NSArray<id<Mappable>> *results))completion { // Load data... // Parse data... if ([mappingClass conformsToProtocol:@protocol(Mappable)]) { id result = [mappingClass initWithDictionary:response]; completion(@[result]); } } @end 14
- 15. RUN TIME!
- 16. What run time means? DataProvider *provider = [DataProvider new]; [provider fetch:@"/users" mappingClass:[NSString class] // compiler doesn’t warn you here... completion:^(NSArray<User *> *results) { }]; 16
- 17. You are doing it wrong with Swift let dataProvider = DataProvider() dataProvider.fetch("/resource", mappingClass: User.self) { result in // code smell... guard let users = result.values as? [User] else { return } } 17
- 18. <T>
- 19. Demo
- 20. UIKit<T>?
- 21. UITableView powered by generics
- 22. 90% of our screens are table views
- 23. 23
- 24. Problems with UITableView • Boilerplate • Painful when data sources are complex and dynamic • Not type safe (dequeueReusableCellWithIdentifier etc.) 24
- 25. What table view actually needs? Model ViewModel UITableViewCell Deadline ;) 25
- 27. What if…
- 28. Line of code let row = TableRow<String, MyTableViewCell>(item: "string") 28
- 29. Demo
- 31. TableKit import TableKit let clickAction = TableRowAction<String, MyTableViewCell>(.click) { (data) in } let row = TableRow<String, MyTableViewCell>(item: "string", actions: [clickAction]) tableDirector += TableSection(rows: [row]) 31
- 33. The power of declarative approach let rows: [Row] = strings.map { TableRow<String, MyTableViewCell>(item: $0) }
- 34. The view layer is simply a mapping of our data layer let rows: [Row] = users .filter({ $0.active }) .map({ UserViewModel(user: $0) }) .map({ TableRow<UserViewModel, UserTableViewCell>(item: $0) })
- 35. Resume • Currently, SDK/API’s are not generic • Compiler is not perfect • Can’t be used with Objective-C • Compile-time type-safety help to know about potential issues earlier • We could build great, flexible, easy to use API’s 35
- 36. Links 36 Covariance and Contravariance https://www.mikeash.com/pyblog/friday-qa-2015-11-20-covariance-and-contravariance.html Protocols with Associated Types, and How They Got That Way http://www.slideshare.net/alexis_gallagher/protocols-with-associated-types-and-how-they-got-that-way Why Associated Types? http://www.russbishop.net/swift-why-associated-types TableKit https://github.com/maxsokolov/TableKit
- 38. THANK YOU!
- 39. QUESTIONS? Max Sokolov - iOS dev @ Avito max_sokolov https://github.com/maxsokolov