An introduction to Reactive programming in iOS with Swift

1. RXSWIFT
REACTIVE PROGRAMMING WITH

2. WHO AM I?
▸ iOS developer since 2010
▸ Swift since day 1
▸ Transitioning to Swift
▸ CocoaConf
▸ Wash U
▸ RayWenderlich.com
▸ lynda.com

3. WHO ARE YOU?
▸ iOS developer
▸ How long?
▸ Swift developer
▸ How long?
▸ Reactive programming
▸ ReactiveCocoa
▸ Reactive Extensions

4. WHAT IS REACTIVE PROGRAMMING?

5. REACTVE PROGRAMMING IS
ESSENTIALLY WORKING WITH
ASYNCHRONOUS DATA STREAMS
@fpillet

6. ABOUT REACTIVE EXTENSIONS
▸ Event-driven
▸ Asynchronous
▸ Functional
▸ Common patterns
▸ Observer
▸ Iterator
▸ Cross-platform

7. CANONICAL EXAMPLE
IMPERATIVE
a = 3
b = 4
c = a + b // 7
a = 6
c // 7

8. CANONICAL EXAMPLE
REACTIVE
a = 3
b = 4
c = a + b
a = 6
c // 10
// 7

9. TRADITIONAL VS. REACTIVE
A SIMPLE EXAMPLE IN IOS

10. MODEL

11. VIEW MODEL

12. VIEW CONTROLLER

14. REACTIVE VIEW MODEL

17. REACTIVE VIEW CONTROLLER

18. THE RESULTS
40% LESS

19. Environment
Interactive
Reactive
Program

20. REACTIVE EXTENSIONS
N
ov.‘09
Rx.N
ET
RxJS
M
ar.‘10
RxJava
M
ar.‘12
RxC
pp
N
ov.‘12
RxRuby
D
ec.‘12
RxScala,RxC
lojure,RxG
roovy,RxJRuby
Jan.‘13
RxPY,RxPH
P
M
ar.‘13
RxKotlin
O
ct.‘13
RxSw
ift
Feb.‘15

21. REACTIVE MANIFESTO

22. RX STANDARDIZES THE
PATTERNS & OPERATORS
USED TO DEVELOP
ASYNCHRONOUS APPS IN
MULTIPLE
ENVIRONMENTS.

25. RXSWIFT OPERATORS
▸ Creating
asObservable
create
deferred
empty
error
toObservable
interval
never
just
of
range
repeatElement
timer
▸ Transforming
buffer
flatMap
flatMapFirst
flatMapLatest
map
scan
window
▸ Filtering
debounce / throttle
distinctUntilChanged
elementAt
filter
sample
skip
take
takeLast
single
▸ Conditional & Boolean
amb
skipWhile
skipUntil
takeUntil
takeWhile
▸ Mathematical &
Aggregate
concat
reduce
toArray
▸ Connectable
multicast
publish
refCount
replay
shareReplay
▸ Combining
merge
startWith
switchLatest
combineLatest
zip
▸ Error Handling
catch
retry
retryWhen
▸ Observing
delaySubscription
do / doOnNext
observeOn
subscribe
subscribeOn
timeout
using
debug

26. LIFECYCLE OF AN OBSERVABLE (AKA SEQUENCE)
▸ onNext
▸ onError
▸ onComplete
▸ dispose() / DisposeBag

27. DO YOU HAZ TEH
CODEZ ?!?

28. SETUP
▸ Install ThisCouldBeUsButYouPlaying
▸ bit.ly/podsPlaygrounds
▸ gem install cocoapods-playgrounds
▸ Create RxSwiftPlayground
▸ pod playgrounds RxSwift

29. SETUP
//: Please build the scheme 'RxSwiftPlayground' first
import XCPlayground
XCPlaygroundPage.currentPage.needsIndefiniteExecution = true
import RxSwift

30. SETUP
//: Please build the scheme 'RxSwiftPlayground' first
import XCPlayground
XCPlaygroundPage.currentPage.needsIndefiniteExecution = true
import RxSwift
func exampleOf(description: String, action: Void -> Void) {
print("n--- Example of:", description, "---")
action()
}

31. --- Example of: just ---
Next(32)
Completed
exampleOf("just") {
Observable.just(32)
.subscribe {
print($0)
}
}
CREATING & SUBSCRIBING

32. --- Example of: just ---
Next(32)
Completed
exampleOf("just") {
Observable.just(32)
.subscribe { value in
print(value)
}
}
CREATING & SUBSCRIBING

33. --- Example of: just ---
32
exampleOf("just") {
_ = Observable.just(32).subscribeNext { print($0) }
}
CREATING & SUBSCRIBING

34. --- Example of: of ---
1
2
3
4
5
exampleOf("of") {
Observable.of(1, 2, 3, 4, 5)
.subscribeNext {
print($0)
}
.dispose()
}
CREATING & SUBSCRIBING

35. --- Example of: toObservable ---
1
2
3
exampleOf("toObservable") {
let disposeBag = DisposeBag()
[1, 2, 3].toObservable()
.subscribeNext {
print($0)
}
.addDisposableTo(disposeBag)
}
CREATING & SUBSCRIBING

36. --- Example of: BehaviorSubject ---
Next(Hello)
Next(World!)
exampleOf("BehaviorSubject") {
let disposeBag = DisposeBag()
let string = BehaviorSubject(value: "Hello")
string.subscribe {
print($0)
}
.addDisposableTo(disposeBag)
string.onNext("World!")
}
CREATING & SUBSCRIBING

37. CREATING & SUBSCRIBING
--- Example of: Variable ---
Next(1)
Next(12)
Next(1234567)
Completed
exampleOf("Variable") {
let disposeBag = DisposeBag()
let number = Variable(1)
number.asObservable()
.subscribe {
print($0)
}
.addDisposableTo(disposeBag)
number.value = 12
number.value = 1_234_567
}

38. exampleOf("map") {
Observable.of(1, 2, 3)
.map { $0 * $0 }
.subscribeNext { print($0) }
.dispose()
}
TRANSFORMING
--- Example of: map ---
1
4
9

39. TRANSFORMING
--- Example of: Variable and map ---
one
twelve
one million two hundred thirty-four thousand five hundred sixty-seven
exampleOf("Variable and map") {
let disposeBag = DisposeBag()
let numberFormatter = NSNumberFormatter()
numberFormatter.numberStyle = .SpellOutStyle
let number = Variable(1)
number.asObservable()
.map { numberFormatter.stringFromNumber($0)! }
.subscribeNext { print($0) }
.addDisposableTo(disposeBag)
number.value = 12
number.value = 1_234_567
}

40. TRANSFORMING
--- Example of: flatMap ---
Scott
Lori
Eric
exampleOf("flatMap") {
let disposeBag = DisposeBag()
struct Person {
var name: Variable<String>
}
let scott = Person(name: Variable("Scott"))
let lori = Person(name: Variable("Lori"))
let person = Variable(scott)
person.asObservable()
.flatMap {
$0.name.asObservable()
}
.subscribeNext {
print($0)
}
.addDisposableTo(disposeBag)
person.value = lori
scott.name.value = "Eric"
}

41. TRANSFORMING
--- Example of: flatMapLatest ---
Scott
Lori
exampleOf("flatMap") {
let disposeBag = DisposeBag()
struct Person {
var name: Variable<String>
}
let scott = Person(name: Variable("Scott"))
let lori = Person(name: Variable("Lori"))
let person = Variable(scott)
person.asObservable()
.flatMapLatest {
$0.name.asObservable()
}
.subscribeNext {
print($0)
}
.addDisposableTo(disposeBag)
person.value = lori
scott.name.value = "Eric"
}

43. exampleOf("distinctUntilChanged") {
let disposeBag = DisposeBag()
let searchString = Variable("iOS")
searchString.asObservable()
.map { $0.lowercaseString }
.distinctUntilChanged()
.subscribeNext { print($0) }
.addDisposableTo(disposeBag)
searchString.value = "IOS"
searchString.value = "Rx"
searchString.value = "ios"
}
FILTERING
--- Example of: distinctUntilChanged ---
ios
rx
ios

44. exampleOf("combineLatest") {
let disposeBag = DisposeBag()
let number = PublishSubject<Int>()
let string = PublishSubject<String>()
Observable.combineLatest(number, string) { "($0) ($1)" }
.subscribeNext { print($0) }
.addDisposableTo(disposeBag)
number.onNext(1)
print("Nothing yet")
string.on(.Next("A"))
number.onNext(2)
string.onNext("B")
string.onNext("C")
}
COMBINING
--- Example of: combineLatest ---
Nothing yet
1 A
2 A
2 B
2 C

45. exampleOf("takeWhile") {
[1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1].toObservable()
.takeWhile { $0 < 5 }
.subscribeNext { print($0) }
.dispose()
}
CONDITIONAL
--- Example of: takeWhile ---
1
2
3
4

46. MATHEMATICAL
--- Example of: reduce ---
1024
exampleOf("reduce") {
[1, 2, 4, 8, 16].toObservable()
.reduce(1, accumulator: *)
.subscribeNext { print($0) }
.dispose()
}

47. ERROR HANDLING
--- Example of: error ---
A
exampleOf("error") {
enum Error: ErrorType { case A }
Observable<Int>.error(Error.A)
.subscribeError {
// Handle error
print($0)
}
.dispose()
}

48. RXMARBLES

49. RXSWIFTPLAYER

50. OBJECTIONS
1. Dependency
2. Complexity
3. Performance
4. Debugging
5. Help

51. BENEFITS
1. Write less, do more
2. Avoid mutable state errors
3. Learn once, apply everywhere
4. Mix in or go all in
5. “It reads almost like a paragraph”
6. Easy to test and heavily tested

52. QUESTIONS?

53. WANT MORE RX?
▸ github.com/ReactiveX/RxSwift
▸ reactivex.io
▸ rxmarbles.com
▸ rxswift.slack.com
▸ rx-marin.com
▸ http://as.ync.io
▸ github.com/scotteg/RxSwiftPlayer
▸ github.com/Artsy/eidolon

54. THANK YOU!
Scott Gardner
@scotteg
as.ync.io
bit.ly/scottOnLyndaDotCom