1. Introduction to
Functional Reactive
Programming
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2. About me
Eliasz Sawicki
Blog: www.eliaszsawicki.com
Twitter: @EliSawic
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3. Agenda
• What is functional reactive programming?
• Working with streams
• ReactiveSwift - Thinking in signals
• Example
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4. Functional Reactive Programming
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5. Wikipedia
Functional reactive programming (FRP) is a programming
paradigm for reactive programming (asynchronous dataflow
programming) using the building blocks of functional
programming (e.g. map, reduce, filter).
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6. Reactive
Programming
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7. Functional
Programming
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8. Blocks
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9. Imperative
vs
Declarative
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10. Imperative
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11. Imperative
let array = [0, 1, 2, 3, 4, 5]
var evenNumbers = [Int]()
for element in array {
if element % 2 == 0 {
evenNumbers.append(element)
}
}
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12. Declarative
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13. Declarative
let array = [0, 1, 2, 3, 4, 5]
let evenNumbers = array.filter { $0 % 2 == 0 }
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14. Working with streams
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15. Stream
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16. Manipulating streams
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17. Map
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18. Filter
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19. Aggregating
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20. Manipulating
multiple streams
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21. Combine latest
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22. Merge
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23. Chaining streams
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24. www.rxmarbles.com
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25. ReactiveSwift
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26. Thinking in Signals
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27. What is a signal?
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28. This screen is a signal
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29. Represents events
over time
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30. Observing does not
trigger side effects
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31. No random access to
events
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32. Observe
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33. If you don't listen, it's
gone
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34. What is event?
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35. Event
struct Idea {
var content: String
var quality: Quality
}
enum Quality {
case Great
case Average
case Worst
}
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36. Non-Terminating
• Next
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37. Terminating
• Completed
• Failed
• Interrupted (Reactive Cocoa)
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38. Presentation
let (presentation, presentationObserver) = Signal<Idea, NoError>.pipe()
let content = "This presentation is a signal"
let idea = Idea(content: content, quality: .Great)
presentationObserver.send(value: idea)
presentationObserver.sendCompleted()
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39. Observing
presentation.observeValues { idea in
remember(idea: idea)
}
presentation.observeCompleted {
print("Time for a break")
}
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40. Only great ideas
let greatIdeas = presentation.filter { idea in
idea.quality == .Great
}
greatIdeas.observeValues { greatIdea in
remember(idea: greatIdea)
}
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41. Positive listener
let greatPresentation = presentation.map { idea -> Idea in
var greatIdea = idea
greatIdea.quality = .Great
return greatIdea
}
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42. Signal producer
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43. Represents a tasks
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44. Possible side effects
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45. Does not start it's
work if not asked
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46. Run presentation
func runPresentation() -> SignalProducer<Idea, NoError> {
return SignalProducer { observer, _ in
observer.send(value: idea1)
observer.send(value: idea2)
...
observer.sendCompleted()
}
}
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47. Work with presentation
runPresentation().startWithValues { idea in
print(idea)
}
runPresentation().startWithSignal { (signal, _) in
signal.observeValues({ idea in
print(idea)
})
signal.observeCompleted {
print("Finally...")
}
}
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48. Cold vs Hot
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49. Properties
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50. Mutable Property
let firstSlide = Slide(number: 1)
let slide = MutableProperty<Slide>(firstSlide)
slide.producer.startWithValues { (text) in
print(text)
}
slide.value = Slide(number: 2)
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51. Bindings
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52. Binding example
let slideNumber = MutableProperty<Int>(0)
let (signal, _) = Signal<Slide, NoError>.pipe()
slideNumber <~ signal.map { return $0.number }
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53. Binding example
let (signal, _) = Signal<Slide, NoError>.pipe()
label.reactive.text <~ signal.map { return "Slide: ($0.number)" }
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54. Schedulers
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55. Know where you are
signal.observe(on: QueueScheduler.main).observeValues { idea in
print("Performing UI updates")
}
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56. Memory Management
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57. Disposables
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58. Free your memory
let disposable = signal.observeValues { value in
...
}
disposable.dispose()
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59. Release your producers
let disposable = producer.startWithValues { value in
...
}
disposable.dispose()
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60. Example
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61. @EliSawic

62. How does it work?
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63. Is name valid?
let isValidNameSignal = nameSignal.map { (name) -> Bool in
return name.characters.count > 2
}
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64. Is surname valid?
let isValidSurnameSignal = surnameSignal.map { (surname) -> Bool in
return surname.characters.count > 2
}
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65. Is mail valid?
let isValidMailSignal = mailSignal.map { (mail) -> Bool in
let emailRegEx = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+.[A-Za-z]{2,}"
let emailTest = NSPredicate(format:"SELF MATCHES %@", emailRegEx)
return emailTest.evaluateWithObject(mail)
}
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66. Combine Latest
let formDataSignal = combineLatest(
isValidNameSignal,
isValidSurnameSignal,
isValidMailSignal)
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67. Is form valid?
let isValidFormSignal = formDataSignal.map {
(isValidName, isValidSurname, isValidMail) -> Bool in
return isValidMail && isValidSurname && isValidMail
}
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68. Update the state
isValidFormSignal.observeValues { isValid in
updateButtonWith(state: isValid)
}
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69. Binding
let isValidForm = MutableProperty<Bool>(false)
isValidForm <~ isFormValidSignal
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70. Conclusion
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71. Thank you for your
attention!
sendCompleted()
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