Leverage RxSwift with VIPER to make your code more reactive with less state handling.

1. Reactive VIPER
IVAN ĐIKIĆ

2. WHY?

3. UIVIEWCONTROLLER
(UIVIEW)

4. • workhorse
• hard to test
• hard to maintain
• not reusable
BUILDING BLOCK FOR COCOA TOUCH

5. VIPER

6. • in 4 parts
• good for medium to big size applications
• good separation of responsibility
• loosely coupled components
SPLIT UP VIEW CONTROLLER

7. • connection between components is achieved using protocols
• composition instead inheritance in most cases
• most of UI is done in Storyboards but without Segues
GENERAL

8. • View / View Controller
• Presenter (view model :))
• Interactor
• Wireframe
MAIN COMPONENTS

9. MAIN COMPONENTS

10. MAIN COMPONENTS

11. • business logic agnostic
• knows how to layout itself
• reusable
VIEW / VIEW CONTROLLER

12. • business logic
• least reusable part
• has reference to
• view
• interactor
• wireframe
• models data received from interactor
• views delegate (responds to view events)
PRESENTER

13. • has the data
• knows how to get the data
INTERACTOR

14. • knows how to navigate
• knows how to create other VIPER modules
WIREFRAME

15. RX(SWIFT)

16. • FRP
• functional programming
• functions don’t have side effects, no mutable state
• difficult to program since real world is all about side effects
• reactive programming
• changes propagate throughout a system automatically
• functional reactive programming
• we model user input as a function that changes over time,
abstracting away the idea of mutable state
CREATED BY MICROSOFT (RX.NET)

17. • sweet spot between functional and imperative programming world
• unifies various design patterns (GoF)
• Delegate
• Callback (Closures, Blocks)
• KVO
• Notifications
• Observer
• enables building apps in declarative style
WHY RX?

18. DECLARATIVE STYLE
Observable
.combineLatest
(
firstName.rx_text,
lastName.rx_text
)
{
$0 + " " + $1
}
.map {
"Greetings, ($0)"
}
.bindTo(greetingLabel.rx_text)

19. ITERATOR, OBSERVER

20. Observer and Iterator patterns are mathematical duals
CORE KNOWLEDGE

21. ITERATOR PATTERN

22. • pull based interface
• good for traversing collections
• standard interface
• generator
• next (pull)
• no more data
• throw (error)
• arrays, dictionaries, sets
ITERATOR

23. • a collection of protocols
• CollectionType
• SequenceType
• GeneratorType
ITERATOR IN SWIFT

24. GeneratorType
- serve elements
protocol GeneratorType {
associatedtype Element
mutating func next() -> Element?
}

25. SequenceType
- knows how to create generator
struct PrefixSequence: SequenceType {
let string: String
func generate() -> PrefixGenerator {
return PrefixGenerator(string: string)
}
}

26. CollectionType
- repeatable iteration
- access to the elements via index
struct BeersCollection<T> {
let beers: [T]
}

27. CollectionType
extension BeersCollection: SequenceType {
typealias Generator = AnyGenerator<T>
func generate() -> AnyGenerator<T> {
var i = 0
return AnyGenerator {
i += 1
return i >= self.beers.count
?
nil
:
self.beers[i]
}
}
}

28. OBSERVER PATTERN

29. • push based interface
• good for UI events
• missing
• error handling
• no more data
OBSERVER

30. Observer
protocol PropertyObserver : class {
func willChangePropertyName(propertyName: String, newPropertyValue: AnyObject?)
func didChangePropertyName(propertyName: String, oldPropertyValue: AnyObject?)
}

31. Observer
class TestChambers {
weak var observer: PropertyObserver?
var testChamberNumber: Int = 0 {
willSet(newValue) {
observer?.willChangePropertyName("testChamberNumber", newPropertyValue:newValue)
}
didSet {
observer?.didChangePropertyName("testChamberNumber", oldPropertyValue:oldValue)
}
}
}

32. OBSERVABLES
AKA
SEQUENCES

33. • unifying Iterator and Observer pattern
• can be composed
• we already know how to do operations on collections
• map
• filter
• reduce
• the equivalence of observer pattern (Observable<Element>
sequence) and normal sequences (SequenceType) is the most
important thing to understand about Rx
GENERAL

34. • every observable sequence is just a sequence
• push interface (aka callback)
• regex
• next* (error | completed)?
• can have 0 or more elements
• once error or completed
• sequence cannot produce any other element
• all internal resources will be disposed
• no work will be performed until you call subscribe
OBSERVABLES AKA SEQUENCES

35. TIPS’N’TRICKS

36. RTFM

37. AVOID NESTING CALLS

38. ALWAYS USE `DISPOSE BAG`

39. `SOURCEKIT` HAS CRASHED

40. USE [WEAK SELF]

41. PERIODICALLY PRINT RESOURCES
COUNT

42. STRIVE TO MODEL YOUR SYSTEMS AS
PURE FUNCTIONS

43. RESOURCES

44. RESOURCES
• RxSwift
• Reactive Programming Overview
• Design Patterns In Swift
• Inside .Net Reactive Framework
• Duality
• Visual Operators (RxMarbles)

45. Q&A