Dependency Injection Pattern for iOS Apps

FrenchKit 2018 in Paris, September 20-21, 2018
https://frenchkit.fr/

Transcript

1. !ZPJDIJUHZ Dependency Injection Pattern for iOS Apps Yoichi Tagaya FrenchKit, 20-21 September, 2018
2. !ZPJDIJUHZ Yoichi Tagaya, from Tokyo, Japan About me
3. !ZPJDIJUHZ Tokyo evening view 1IPUP
   CZ
   D
   5PNP:VO
   IUUQXXXZVOQIPUPOFU
4. !ZPJDIJUHZ About me as Swinject author • Swinject: dependency injection framework for Swift • Maintained by 5 members • Recently by Jakub Vano especially! • 2,6k+ GitHub stars now and 1k clones everyday • 4 extensions provided
5. !ZPJDIJUHZ Agenda • Software architecture • Dependency injection (DI) • Swinject (DI container)
6. !ZPJDIJUHZ What is software architecture
7. !ZPJDIJUHZ What is software architecture
   IUUQTXXXJCNDPNEFWFMPQFSXPSLTSBUJPOBMMJCSBSZGFCFFMFTJOEFYIUNM
8. !ZPJDIJUHZ Peter Eeles says An architecture • Defines structure and behavior • Focuses on significant elements • May conform to an architectural style • Influences team structure (inverse Conway maneuver) • Balances stakeholder needs • Is influenced by its environment • Embodies decisions based on rationale
9. !ZPJDIJUHZ Architecture is not static but dynamic .7$ "SDIJUFDUVSF :FBST
   TJODF
   MBVODI  .77.  7*1&3  &YBNQMF
   PG
   B
   QSPEVDU 3*#T &OHJOFFST     6TFST  L . . 
10. !ZPJDIJUHZ Architecture is not static but dynamic $ # " /PX $ /FX
    # " $ % -BUFS
11. !ZPJDIJUHZ Production / unit test $ # " 1SPEVDUJPO 6OJU
    5FTU .PDLTUVC
    PG
    # "
12. !ZPJDIJUHZ We need flexibility in architecture
13. !ZPJDIJUHZ How to make architecture flexible? Dependency injection!
14. !ZPJDIJUHZ Because dependency injection is glue but sticky-like glue 5JHIU
    $PVQMJOH -PPTF
    $PVQMJOH
15. !ZPJDIJUHZ How to make the sticky-like glue?
16. !ZPJDIJUHZ SOLID principles • S - Single responsibility principle • O - Open/closed principle • L - Liskov substitution principle • I - Interface segregation principle • D - Dependency inversion principle • Should not depend on concretions but abstractions
17. !ZPJDIJUHZ Depending on concretions / abstractions Depending on concretions (tight coupling) *NQMFNFOUBUJPO $PODSFUF
    5ZQF Depending on abstractions (loose coupling) 3FGFSFODF *NQMFNFOUBUJPO Protocol (Interface) 3FGFSFODF $PODSFUF
    5ZQF
    " $PODSFUF
    5ZQF
    #
18. !ZPJDIJUHZ Dependency injection: a way to realize dependency inversion principle *NQMFNFOUBUJPO Protocol (Interface) 3FGFSFODF *OTUBODF
    PG
    $PODSFUF
    5ZQF
    # 1BTT
    JOKFDU
    UP
    JOJUJBMJ[FS
19. !ZPJDIJUHZ Dependency injection: a way to realize dependency inversion principle *NQMFNFOUBUJPO Protocol (Interface) 3FGFSFODF $PODSFUF
    5ZQF
    # 5IF
    TZTUFN
    JT
    DPOpHVSFE
    UP
    VTF
    $PODSFUF
    5ZQF
    #
20. !ZPJDIJUHZ Code example of dependency injection protocol APIClientProtocol { ... } class APIClient: APIClientProtocol { ... } let vm = MyViewModel(apiClient: APIClient()) class MyViewModel { let apiClient: APIClientProtocol init(apiClient: APIClientProtocol) { self.apiClient = apiClient } } APIClientProtocol "CTUSBDU
    UZQF *OKFDU
    DPODSFUF
    UZQF
21. !ZPJDIJUHZ Try dependency injection with Swinject Register/resolve-style DI container like dictionary
22. !ZPJDIJUHZ How to use Swinject container $POUBJOFS Register Resolve
23. !ZPJDIJUHZ Code example of registration $POUBJOFS Register import Swinject let container = Container() container.register(MyViewModel.self) { resolver in let apiClient = resolver.resolve(APIClientProtocol.self)! return MyViewModel(apiClient: apiClient) } container.register(APIClientProtocol.self) { _ in APIClient() }
24. !ZPJDIJUHZ Code example of resolution $POUBJOFS Resolve import Swinject let vm = container.resolve(MyViewModel.self)!
25. !ZPJDIJUHZ It’s ok for a simple case, but…
26. !ZPJDIJUHZ In a production app class MyViewModel { init(dep1: D1, dep2: D2, dep3: D3, id: String, name: String) { ... } } .BOZ
    EFQFOEFODJFT 3VOUJNF
    QBSBNFUFST
    PUIFS
    UIBO
    EFQFOEFODJFT %FQFOEFODZ
    JOKFDUJPO
    DPEF
    JT
    PGUFO
    MJLF
    UIJT
27. !ZPJDIJUHZ Using typealias of dependency tuple init(dependency: Dependency, id: String, name: String) 5ZQFBMJBT
    PG
    UVQMF
    %
    %
    % %FQFOEFODZ 1BSBNFUFST
28. !ZPJDIJUHZ Example of class definition with typealias of tuple protocol APIClientProtocol { ... } class APIClient: APIClientProtocol { ... } protocol LoggerProtocol { ... } class Logger: LoggerProtocol { ... } 5ZQFBMJBT
    PG
    EFQFOEFODZ
    UVQMF class MyViewModel { typealias Dependency = ( APIClientProtocol, LoggerProtocol ) let (apiClient, logger): Dependency let id: String init(dependency: Dependency, id: String) { (apiClient, logger) = dependency self.id = id } } &YBNQMF
    XJUI
    
    EFQFOEFODJFT
    BOE
    
    QBSBNFUFS
29. !ZPJDIJUHZ DI Registration let container = Container() container.register(APIClientProtocol.self) { _ in APIClient() } container.register(LoggerProtocol.self) { _ in Logger() } $POUBJOFS Register container.register(MyViewModel.self) { (resolver, id: String) in let dependency = ( resolver.resolve(APIClientProtocol.self)!, resolver.resolve(LoggerProtocol.self)! ) return MyViewModel( dependency: dependency, id: id ) }
30. !ZPJDIJUHZ DI Resolution let myViewModel = container.resolve( MyViewModel.self, argument: "abc")! $POUBJOFS Resolve
31. !ZPJDIJUHZ Easier to see the dependencies and parameters!
32. !ZPJDIJUHZ Let’s add another dependency to implement a new feature
33. !ZPJDIJUHZ Add another dependency let (apiClient, logger): Dependency let id: String init(dependency: Dependency, id: String) { (apiClient, logger) = dependency self.id = id } } class MyViewModel { typealias Dependency = ( APIClientProtocol, LoggerProtocol )
34. !ZPJDIJUHZ Add another dependency protocol DatabaseProtocol { ... } class Database: DatabaseProtocol { ... } let (apiClient, logger): Dependency let id: String init(dependency: Dependency, id: String) { (apiClient, logger) = dependency self.id = id } } class MyViewModel { typealias Dependency = ( APIClientProtocol, LoggerProtocol )
35. !ZPJDIJUHZ Add another dependency protocol DatabaseProtocol { ... } class Database: DatabaseProtocol { ... } class MyViewModel { typealias Dependency = ( APIClientProtocol, LoggerProtocol, DatabaseProtocol ) let (apiClient, logger): Dependency let id: String init(dependency: Dependency, id: String) { (apiClient, logger) = dependency self.id = id } }
36. !ZPJDIJUHZ Add another dependency protocol DatabaseProtocol { ... } class Database: DatabaseProtocol { ... } class MyViewModel { typealias Dependency = ( APIClientProtocol, LoggerProtocol, DatabaseProtocol ) let (apiClient, logger): Dependency let id: String init(dependency: Dependency, id: String) { (apiClient, logger) = dependency self.id = id } } 8SPOH
    UVQMF
    IFSF ❕
37. !ZPJDIJUHZ Add another dependency protocol DatabaseProtocol { ... } class Database: DatabaseProtocol { ... } class MyViewModel { typealias Dependency = ( APIClientProtocol, LoggerProtocol, DatabaseProtocol ) let (apiClient, logger, database): Dependency let id: String init(dependency: Dependency, id: String) { (apiClient, logger) = dependency self.id = id } } 8SPOH
    UVQMF
    IFSF ❕
38. !ZPJDIJUHZ Add another dependency protocol DatabaseProtocol { ... } class Database: DatabaseProtocol { ... } class MyViewModel { typealias Dependency = ( APIClientProtocol, LoggerProtocol, DatabaseProtocol ) let (apiClient, logger, database): Dependency let id: String init(dependency: Dependency, id: String) { (apiClient, logger, database) = dependency self.id = id } } 8SPOH
    UVQMF
    IFSF ❕
39. !ZPJDIJUHZ Add another dependency protocol DatabaseProtocol { ... } class Database: DatabaseProtocol { ... } class MyViewModel { typealias Dependency = ( APIClientProtocol, LoggerProtocol, DatabaseProtocol ) let (apiClient, logger, database): Dependency let id: String init(dependency: Dependency, id: String) { (apiClient, logger, database) = dependency self.id = id } }
40. !ZPJDIJUHZ Add another dependency container.register(MyViewModel.self) { (resolver, id: String) in let dependency = ( resolver.resolve(APIClientProtocol.self)!, resolver.resolve(LoggerProtocol.self)! ) return MyViewModel( dependency: dependency, id: id ) } let myViewModel = container.resolve( MyViewModel.self, argument: "abc")! $BOOPU
    DPOWFSU ❕
41. !ZPJDIJUHZ Add another dependency container.register(MyViewModel.self) { (resolver, id: String) in let dependency = ( resolver.resolve(APIClientProtocol.self)!, resolver.resolve(LoggerProtocol.self)! ) return MyViewModel( dependency: dependency, id: id ) } let myViewModel = container.resolve( MyViewModel.self, argument: "abc")! container.register(DatabaseProtocol.self) { _ in Database() } $BOOPU
    DPOWFSU ❕
42. !ZPJDIJUHZ Add another dependency container.register(DatabaseProtocol.self) { _ in Database() } $BOOPU
    DPOWFSU ❕ container.register(MyViewModel.self) { (resolver, id: String) in let dependency = ( resolver.resolve(APIClientProtocol.self)!, resolver.resolve(LoggerProtocol.self)!, resolver.resolve(DatabaseProtocol.self)! ) return MyViewModel( dependency: dependency, id: id ) } let myViewModel = container.resolve( MyViewModel.self, argument: "abc")!
43. !ZPJDIJUHZ Add another dependency container.register(DatabaseProtocol.self) { _ in Database() } container.register(MyViewModel.self) { (resolver, id: String) in let dependency = ( resolver.resolve(APIClientProtocol.self)!, resolver.resolve(LoggerProtocol.self)!, resolver.resolve(DatabaseProtocol.self)! ) return MyViewModel( dependency: dependency, id: id ) } let myViewModel = container.resolve( MyViewModel.self, argument: "abc")!
44. !ZPJDIJUHZ Just follow what Swift compiler says to add new dependencies!
45. !ZPJDIJUHZ Summary • Architecture is not static but dynamic to evolve. • Dependency injection is sticky-like glue. • Use a typealias to group dependencies. • Just follow Swift compiler to add new dependencies.
46. !ZPJDIJUHZ More info, merci beaucoup! • Swinject Tutorial for iOS: Getting Started by Gemma Barlow at raywenderlich.com • iOS App Development: Design Patterns for Mobile Architecture by Jon Bott at lynda.com • Dependency injection in Swift by Manuel Munoz at blog.quadiontech.com • Adventures in Dependency Swinjection by Ben Dietzkis at medium.com/@topLayoutGuide • Swinject - Dependency Injection in iOS by Iron Ben Zvi at speakerdeck.com/oronbz