Update Combining Operators and move before Transforming Operators
This commit is contained in:
Scott Gardner
parent
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@ -9,278 +9,150 @@
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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 work with multiple source Observables to create a single Observable.
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*/
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/*:
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### `startWith`
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emit a specified sequence of items before beginning to emit the items from the source Observable
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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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[More info in reactive.io website]( 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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let subscription = Observable.of("🐶","🐱","🐭","🐹")
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.startWith("🔴")
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.startWith("🅱️")
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.startWith("🆎")
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.subscribe {
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print($0)
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}
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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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.subscribeNext { print($0) }
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.addDisposableTo(disposeBag)
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}
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/*:
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### `combineLatest`
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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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## `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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when an item is emitted by either of two Observables, combine the latest item emitted by each Observable via a specified function and emit items based on the results of this function
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[More info in reactive.io website]( http://reactivex.io/documentation/operators/combinelatest.html )
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*/
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example("combineLatest 1") {
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let stringObs = PublishSubject<String>()
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let intObs = PublishSubject<Int>()
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_ = Observable.combineLatest(stringObs, intObs) {
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"\($0) \($1)"
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}
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.subscribe {
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print($0)
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}
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stringObs.on(.Next("🅰️"))
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intObs.on(.Next(1))
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stringObs.on(.Next("🅱️"))
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intObs.on(.Next(2))
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}
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//: To produce output, at least one element has to be received from each sequence in arguements.
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example("combineLatest 2") {
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let stringObs = Observable.of("🐶","🐱","🐭","🐹")
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let intObs = Observable.just(2)
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_ = Observable.combineLatest(stringObs, intObs) {
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"\($0) \($1)"
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}
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.subscribe {
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print($0)
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}
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}
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//: Combine latest has versions with more than 2 arguments.
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example("combineLatest 3") {
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let intObs = Observable.just(2)
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let stringObs1 = Observable.of("🐶","🐱","🐭","🐹")
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let stringObs2 = Observable.of("🅰️","🅱️","🆎")
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_ = Observable.combineLatest(intObs, stringObs1, stringObs2) {
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"\($0) \($1) \($2)"
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}
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.subscribe {
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print($0)
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}
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}
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//: Combinelatest version that allows combining sequences with different types.
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example("combineLatest 4") {
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let intObs = Observable.just(2)
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let stringObs = Observable.just("🔴")
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_ = Observable.combineLatest(intObs, stringObs) {
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"\($0) " + $1
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}
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.subscribe {
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print($0)
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}
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}
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//: `combineLatest` extension method for Array of `ObservableType` conformable types
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//: The array must be formed by `Observables` of the same type.
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example("combineLatest 5") {
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let stringObs1 = Observable.just("❤️")
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let stringObs2 = Observable.of("🐶","🐱","🐭","🐹")
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let stringObs3 = Observable.of("🅰️","🅱️","🆎")
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_ = [stringObs1, stringObs2, stringObs3].combineLatest { stringArray -> String in
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stringArray[0] + stringArray[1] + stringArray[2]
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}
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.subscribe { (event: Event<String>) -> Void in
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print(event)
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}
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}
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/*:
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### `zip`
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combine the emissions of multiple Observables together via a specified function and emit single items for each combination based on the results of this function
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[More info in reactive.io website](http://reactivex.io/documentation/operators/zip.html)
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*/
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example("zip 1") {
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let stringObs = PublishSubject<String>()
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let intObs = PublishSubject<Int>()
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_ = Observable.zip(stringObs, intObs) {
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"\($0) \($1)"
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}
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.subscribe {
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print($0)
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}
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stringObs.on(.Next("🔴"))
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intObs.on(.Next(1))
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stringObs.on(.Next("🔵"))
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stringObs.on(.Next("⚪️"))
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intObs.on(.Next(2))
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}
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example("zip 2") {
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let intObs = Observable.just(1)
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let stringObs = Observable.of("🐶","🐱","🐭","🐹")
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_ = Observable.zip(intObs, stringObs) {
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"\($0) \($1)"
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}
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.subscribe {
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print($0)
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}
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}
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example("zip 3") {
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let intObs = Observable.of(1,2)
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let stringObs1 = Observable.of("🐶","🐱","🐭","🐹")
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let stringObs2 = Observable.of("🍎","🍐","🍊","🍋","🍉","🍓")
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_ = Observable.zip(intObs, stringObs1, stringObs2) {
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"\($0) \($1) \($2)"
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}
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.subscribe {
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print($0)
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}
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}
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/*:
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### `merge`
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combine multiple Observables into one by merging their emissions
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[More info in reactive.io website]( http://reactivex.io/documentation/operators/merge.html )
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*/
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example("merge 1") {
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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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Observable.of(subject1, subject2)
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.merge()
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.subscribeNext { string in
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print(string)
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}
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.subscribeNext { print($0) }
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.addDisposableTo(disposeBag)
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subject1.on(.Next("🍎"))
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subject1.on(.Next("🍐"))
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subject1.on(.Next("🍊"))
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subject2.on(.Next("🔴"))
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subject1.on(.Next("🍋"))
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subject1.on(.Next("🍉"))
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subject2.on(.Next("🔵"))
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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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example("merge 2") {
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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(maxConcurrent: 2)
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.subscribe {
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print($0)
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}
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subject1.on(.Next("🍎"))
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subject1.on(.Next("🍐"))
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subject1.on(.Next("🍊"))
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subject2.on(.Next("🔴"))
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subject1.on(.Next("🍋"))
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subject1.on(.Next("🍉"))
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subject2.on(.Next("🔵"))
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}
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/*:
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### `switchLatest`
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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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convert an Observable that emits Observables into a single Observable that emits the items emitted by the most-recently-emitted of those Observables
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let stringSubject = PublishSubject<String>()
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let intSubject = PublishSubject<Int>()
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[More info in reactive.io website]( http://reactivex.io/documentation/operators/switch.html )
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*/
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example("switchLatest") {
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let var1 = Variable("⚽️")
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let var2 = Variable("🍎")
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// var3 is an Observable<Observable<String>>
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let var3 = Variable(var1.asObservable())
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let d = var3
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.asObservable()
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.switchLatest()
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.subscribe {
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print($0)
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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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.subscribeNext { print($0) }
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.addDisposableTo(disposeBag)
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var1.value = "🏀"
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var1.value = "🏈"
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var1.value = "⚾️"
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var1.value = "🎱"
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stringSubject.onNext("🅰️")
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stringSubject.onNext("🅱️")
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var3.value = var2.asObservable()
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intSubject.onNext(1)
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var2.value = "🍐"
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intSubject.onNext(2)
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var1.value = "🏐"
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var1.value = "🏉"
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var2.value = "🍋"
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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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.subscribeNext { 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 = ["🍎", "🍐", "🍊"].toObservable()
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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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.subscribeNext { 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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.subscribeNext { 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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@ -9,9 +9,9 @@
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1. [Introduction](Introduction)
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1. [Creating and Subscribing to Observables](Creating_and_Subscribing_to_Observables)
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1. [Working with Subjects](Working_with_Subjects)
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1. [Combining Operators](Combining_Operators)
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1. [Transforming Operators](Transforming_Operators)
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1. [Filtering Operators](Filtering_Operators)
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1. [Combining Operators](Combining_Operators)
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1. [Conditional Operators](Conditional_Operators)
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1. [Mathematical and Aggregate Operators](Mathematical_and_Aggregate_Operators)
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1. [Connectable Operators](Connectable_Operators)
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@ -54,7 +54,7 @@ example("flatMap and flatMapLatest") {
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👧🏼.score.value = 100
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}
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/*:
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> In the above example, using `flatMap` may have unintended consequences. After assigning 👧🏼 to `player.value`, `👧🏼.score` will begin to emit elements, but the previous inner `Observable` sequence (`👦🏻.score`) will also still emit elements. By changing `flatMap` to `flatMapLatest`, only the most recent inner `Observable` sequence (`👧🏼.score`) will emit elements, i.e., setting `👦🏻.score.value` to `95` has no effect.
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> In this example, using `flatMap` may have unintended consequences. After assigning 👧🏼 to `player.value`, `👧🏼.score` will begin to emit elements, but the previous inner `Observable` sequence (`👦🏻.score`) will also still emit elements. By changing `flatMap` to `flatMapLatest`, only the most recent inner `Observable` sequence (`👧🏼.score`) will emit elements, i.e., setting `👦🏻.score.value` to `95` has no effect.
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#
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> `flatMapLatest` is actually a combination of the `map` and `switchLatest` operators.
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*/
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@ -5,9 +5,9 @@
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<page name='Introduction'/>
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<page name='Creating_and_Subscribing_to_Observables'/>
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<page name='Working_with_Subjects'/>
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<page name='Combining_Operators'/>
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<page name='Transforming_Operators'/>
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<page name='Filtering_Operators'/>
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<page name='Combining_Operators'/>
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<page name='Conditional_Operators'/>
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<page name='Mathematical_and_Aggregate_Operators'/>
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<page name='Connectable_Operators'/>
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