RxSwift Series (four)

Objective

This article will learn about RxSwift the four conversion operators:

• map
• flatMap
• flatMapLatest
• scan

Map

Converts the original Observable sequence to a new sequence by using a closure function Observable .

let disposeBag = DisposeBag()        Observable.of(1,2,3).map({return 10 * $0}).subscribe({print($0)}).disposed(by: disposeBag)

Printing results:

next(10)next(20)next(30)completed

FlatMap

Converts a Observable sequence to another Observable sequence, and merges two Observable sequences. Elements emitted by two sequences are received in chronological order.

let disposeBag = DisposeBag()    struct Player {    var score:Variable<Int>}    let man = Player(score: Variable(80))let women = Player(score: Variable(90))    let player = Variable(man)    player.asObservable().flatMap({$0.score.asObservable()}).subscribe(onNext: {print($0)}).disposed(by: disposeBag)    man.score.value = 85player.value = womenman.score.value = 95women.score.value = 100

Printing results:

80859095100

Flatmaplatest

flatMapLatestThe same way flatMap , a sequence is converted to another sequence, and flatMapLatest only events are emitted from the most recent sequence.

flatMapLatest= map +switchLatest

• Question: Feeling and switchLatest no difference ah. ( is there any big guy to help answer it? )

let disposeBag = DisposeBag()    struct Player {    var score:Variable<Int>}    let man = Player(score: Variable(80))let women = Player(score: Variable(90))    let player = Variable(man)    player.asObservable().flatMapLatest({$0.score.asObservable()}).subscribe(onNext: {print($0)}).disposed(by: disposeBag)    man.score.value = 85player.value = womenman.score.value = 95women.score.value = 100

Printing results:

808590100

Scan

scanis to provide an initialization value, and then use a computed closure to continually process the previous and subsequent elements and return the processing results as a sequence of individual elements Observable .

let disposeBag = DisposeBag()    Observable.of(10, 100, 1000)    .scan(2) { aggregateValue, newValue in        aggregateValue + newValue    }    .subscribe(onNext: { print($0) })    .disposed(by: disposeBag)

Printing results:

121121112

Thanks

If you find the wrong place, welcome to comment, thanks!

RxSwift Series (four)