Software-Architektur/-Design in der iOS-Entwicklung. In der traditionellen iOS-Entwicklung mit MVC (Model View Controller) oder heutzutage “trendigem” MVVM (Model View ViewModel) wird wenig bis keine Rücksicht auf den State (bzw. die Daten) in der App genommen. Das führt oft zu schwer verständlichem, und schlecht wartbarem Code, da alles undefiniert und quer verstreut in der App gemacht wird. Daher ist es essentiell, sich um die Organisation des States in der App zu kümmern. Um das Rad nicht neu zu erfinden, bedienen wir uns an Frameworks/Libraries wie ReSwift*, RxSwift** und die Verbindung der beiden “Technologien” über ReRxSwift***. Diese bieten ein gutes State-Management, was dazu führt, dass der State nur an einer Stelle in der App (im s.g. Store) verwaltet wird und nur kontrolliert (über s.g. Actions/Reducers) verändert werden kann. Über s.g. Subscriptions kann man den aktuellen Stand und Änderungen des States erfahren (z.B. in ViewControllers oder Views). * Swift Implementierung von Redux (JavaScript) ** Swift Implementierung von reactiveX (für quasi jede populäre Programmiersprache verfügbar) *** Swift Implementierung von react-redux (JavaScript)

1. ReRxSwift
or:
how I learned to stop worrying and love the bomb
state

3. MVC

4. model view
view controller
some data
some fancy UI
everything else

5. tab bar
controller
navigation
controller
label and button

6. tab bar
controller
view controller
change data
navigation
controller
view controller
view controller
navigation
controller
view controller
view controller
change data

7. state lives everywhere

8. multiple sources of truth

9. no straight forward
sync mechanism

10. 😭

11. MVVM

12. …the savior?

13. 🤔

14. model view
view controller
some data
some fancy UI
everything else

15. view controller
view model
model view
some data
some fancy UI
everything else
view logic

16. view model did not solve
any problems at all

17. we even introduced one
more “source of truth”

18. …the savior?

19. NOPE

20. 😭

21. and now for something
completely different

22. ReSwift
(inspired by Redux)

23. action
store
w/ state
reducers
view*
some data
business
logic
fancy UI
stuff
*view = view + view controller
subscribe
dispatch
change

24. action
store
w/ state
reducers
view*
subscribe
dispatch
change
*view = view + view controller

25. // define the store
let store = Store<State>(reducer: reducer, state: nil)
// define a state (important: value type)
struct State: StateType {
var data: String = "someData"
}

26. action
store
w/ state
reducers
view*
subscribe
dispatch
change
*view = view + view controller

27. // define an action
struct ChangeData: Action {
let changedData: String
}
// create and dispatch an action
let action = ChangeData(changedData: "changedData")
store.dispatch(action)

28. action
store
w/ state
reducers
view*
subscribe
dispatch
change
*view = view + view controller

29. // reducer: action + state = new state
func reducer(action: Action, state: State?) -> State {
}
*switch is non-exhausting for simplicity
// create a new state if state is nil
var state = state ?? State()
// switch through desired actions
switch action {
case let action as ChangeData:
}
// perform state change
state.data = action.changedData
// return the new state
return state

30. action
store
w/ state
reducers
view*
subscribe
dispatch
change
*view = view + view controller

31. class ReSwiftViewController: UIViewController, StoreSubscriber {
@IBOutlet weak var button: UIButton!
@IBOutlet weak var label: UILabel!
}
// subscribe to store
func setup() {
store.subscribe(self)
}
// receive state updates from store
func newState(state: State) {
self.label.text = state.data
}
// dispatch an action to store
@IBAction func buttonTap(_ sender: Any) {
let action = ChangeData(changedData: "changedData")
store.dispatch(action)
}

32. tab bar
controller
view controller
navigation
controller
view controller
view controller
navigation
controller
view controller
view controller
store
w/ state
change data
change data

33. real separation of
state and view

34. one source of truth

35. unidirectional data flow

36. 😀

37. RxSwift
(ReactiveX)

38. “the observer pattern
done right”

40. event
error
completion
time

41. // define data as a subject ("stream")
let data = PublishSubject<String>()
// subscribe to data
data.asObservable()
.subscribe(onNext: { string in
print("data changed to: (string)")
})
// bind data to label
data.bind(to: label.rx.text)
*disposing is left out for simplicity
// trigger an update
data.onNext("changedData")

42. very easy to
“connect the dots”

43. just subscribe/bind

44. 😀

45. some math…

46. 😱

47. some math…
very basic

48. ReSwift + RxSwift = ?

49. 🤔

50. ReRxSwift(inspired by react-redux)

51. actions
store
w/ states
reducers
view*
*view = view + view controller

52. ViewReRxSwift
“Connection”
ReSwift
actions
store
w/ states
reducers
view*
*view = view + view controller
actions
props

53. ViewReRxSwift
“Connection”
ReSwift
actions
store
w/ states
reducers
view*
actions
props
*view = view + view controller

54. // define props
extension ReRxSwiftViewController: Connectable {
}
struct Props {
let data: String
}
// state to props mapping
private let mapStateToProps = { (state: State) in
}
return ReRxSwiftViewController.Props(
data: state.data
)

55. ViewReRxSwift
“Connection”
ReSwift
actions
store
w/ states
reducers
view*
actions
props
*view = view + view controller

56. // define actions
extension ReRxSwiftViewController: Connectable {
}
struct Actions {
let changeData: (String) -> Void
}
// dispatch to actions mapping
private let mapDispatchToActions = { (dispatch: @escaping DispatchFunction) in
}
return ReRxSwiftViewController.Actions(
changeData: { dispatch(ChangeData(changedData: $0)) }
)

57. ViewReRxSwift
“Connection”
ReSwift
actions
store
w/ states
reducers
view*
actions
props
*view = view + view controller

58. class ReRxSwiftViewController: UIViewController {
@IBOutlet weak var button: UIButton!
@IBOutlet weak var label: UILabel!
}
// set up connection with store and mappings
let connection = Connection(store: store,
mapStateToProps: mapStateToProps,
mapDispatchToActions: mapDispatchToActions)
// establish connection and bind to a label
func setup() {
self.connection.connect()
self.connection.bind(Props.data, to: self.label.rx.text)
}
// dispatch an action
@IBAction func buttonTap(_ sender: Any) {
self.connection.actions.changeData("changedData")
}

59. even better separation
of concerns

60. easy to understand

61. easy to re-use and
unit-test

62. 🤩

63. at a glance

64. fail safe state handling

65. unidirectional data flow

66. UI bindings

67. credits

68. github.com/ReSwift/ReSwift
github.com/ReactiveX/RxSwift
github.com/svdo/ReRxSwift
hackernoon.com/thinking-in-redux-when-all-youve-known-is-mvc-c78a74d35133
gist.github.com/staltz/868e7e9bc2a7b8c1f754
rxmarbles.com
swifting.io/blog/2016/09/07/architecture-wars-a-new-hope
khanlou.com/2014/03/model-view-whatever
sharpfivesoftware.com/2016/07/20/mvvm-is-lipstick-on-a-pig
themetapicture.com/the-life-of-a-software-engineer
https://en.wikipedia.org/wiki/LOLCODE

69. questions?

70. KTHXBYE