Functional reactive programming (FRP) is a programming paradigm that uses functional programming concepts like map, reduce, and filter to build reactive programs that can respond asynchronously to changing data over time. It involves working with streams of events, manipulating streams using functions, and combining multiple streams. ReactiveSwift is an FRP framework for iOS that represents events as signals that can be observed and transformed without side effects. It distinguishes between signals that represent real-time events and signal producers that represent asynchronous tasks.

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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