161 lines
5.9 KiB
Swift
161 lines
5.9 KiB
Swift
/*:
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> # IMPORTANT: To use **Rx.playground**:
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1. Open **Rx.xcworkspace**.
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1. Build the **RxSwift-OSX** scheme (**Product** → **Build**).
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1. Open **Rx** playground in the **Project navigator**.
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1. Show the Debug Area (**View** → **Debug Area** → **Show Debug Area**).
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----
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[Previous](@previous) - [Table of Contents](Table_of_Contents)
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*/
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import RxSwift
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/*:
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# Combination Operators
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Operators that combine multiple source `Observable`s into a single `Observable`.
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## `startWith`
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Emits the specified sequence of elements before beginning to emit the elements from the source `Observable`. [More info](http://reactivex.io/documentation/operators/startwith.html)
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*/
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example("startWith") {
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let disposeBag = DisposeBag()
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Observable.of("🐶", "🐱", "🐭", "🐹")
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.startWith("1️⃣")
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.startWith("2️⃣")
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.startWith("3️⃣", "🅰️", "🅱️")
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.subscribe(onNext: { print($0) })
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.addDisposableTo(disposeBag)
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}
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/*:
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> As this example demonstrates, `startWith` can be chained on a last-in-first-out basis, i.e., each successive `startWith`'s elements will be prepended before the prior `startWith`'s elements.
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----
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## `merge`
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Combines elements from source `Observable` sequences into a single new `Observable` sequence, and will emit each element as it is emitted by each source `Observable` sequence. [More info](http://reactivex.io/documentation/operators/merge.html)
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*/
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example("merge") {
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let disposeBag = DisposeBag()
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let subject1 = PublishSubject<String>()
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let subject2 = PublishSubject<String>()
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Observable.of(subject1, subject2)
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.merge()
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.subscribe(onNext: { print($0) })
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.addDisposableTo(disposeBag)
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subject1.onNext("🅰️")
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subject1.onNext("🅱️")
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subject2.onNext("①")
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subject2.onNext("②")
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subject1.onNext("🆎")
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subject2.onNext("③")
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}
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/*:
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----
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## `zip`
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Combines up to 8 source `Observable` sequences into a single new `Observable` sequence, and will emit from the combined `Observable` sequence the elements from each of the source `Observable` sequences at the corresponding index. [More info](http://reactivex.io/documentation/operators/zip.html)
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*/
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example("zip") {
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let disposeBag = DisposeBag()
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let stringSubject = PublishSubject<String>()
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let intSubject = PublishSubject<Int>()
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Observable.zip(stringSubject, intSubject) { stringElement, intElement in
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"\(stringElement) \(intElement)"
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}
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.subscribe(onNext: { print($0) })
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.addDisposableTo(disposeBag)
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stringSubject.onNext("🅰️")
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stringSubject.onNext("🅱️")
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intSubject.onNext(1)
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intSubject.onNext(2)
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stringSubject.onNext("🆎")
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intSubject.onNext(3)
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}
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/*:
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----
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## `combineLatest`
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Combines up to 8 source `Observable` sequences into a single new `Observable` sequence, and will begin emitting from the combined `Observable` sequence the latest elements of each source `Observable` sequence once all source sequences have emitted at least one element, and also when any of the source `Observable` sequences emits a new element. [More info](http://reactivex.io/documentation/operators/combinelatest.html)
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*/
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example("combineLatest") {
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let disposeBag = DisposeBag()
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let stringSubject = PublishSubject<String>()
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let intSubject = PublishSubject<Int>()
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Observable.combineLatest(stringSubject, intSubject) { stringElement, intElement in
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"\(stringElement) \(intElement)"
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}
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.subscribe(onNext: { print($0) })
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.addDisposableTo(disposeBag)
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stringSubject.onNext("🅰️")
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stringSubject.onNext("🅱️")
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intSubject.onNext(1)
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intSubject.onNext(2)
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stringSubject.onNext("🆎")
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}
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//: There is also a `combineLatest` extension on `Array`:
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example("Array.combineLatest") {
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let disposeBag = DisposeBag()
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let stringObservable = Observable.just("❤️")
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let fruitObservable = Observable.from(["🍎", "🍐", "🍊"])
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let animalObservable = Observable.of("🐶", "🐱", "🐭", "🐹")
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[stringObservable, fruitObservable, animalObservable].combineLatest {
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"\($0[0]) \($0[1]) \($0[2])"
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}
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.subscribe(onNext: { print($0) })
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.addDisposableTo(disposeBag)
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}
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/*:
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> The `combineLatest` extension on `Array` requires that all source `Observable` sequences are of the same type.
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----
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## `switchLatest`
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Transforms the elements emitted by an `Observable` sequence into `Observable` sequences, and emits elements from the most recent inner `Observable` sequence. [More info](http://reactivex.io/documentation/operators/switch.html)
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*/
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example("switchLatest") {
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let disposeBag = DisposeBag()
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let subject1 = BehaviorSubject(value: "⚽️")
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let subject2 = BehaviorSubject(value: "🍎")
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let variable = Variable(subject1)
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variable.asObservable()
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.switchLatest()
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.subscribe(onNext: { print($0) })
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.addDisposableTo(disposeBag)
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subject1.onNext("🏈")
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subject1.onNext("🏀")
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variable.value = subject2
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subject1.onNext("⚾️")
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subject2.onNext("🍐")
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}
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/*:
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> In this example, adding ⚾️ onto `subject1` after setting `variable.value` to `subject2` has no effect, because only the most recent inner `Observable` sequence (`subject2`) will emit elements.
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*/
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//: [Next](@next) - [Table of Contents](Table_of_Contents)
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