RxSwift Series (vi)

Objective

This article will learn RxSwift about the math and set operators, which are included in the RxSwift :

• toArray
• reduce
• concat

ToArray

Converts a Observable sequence into an array and converts it to a new Observable sequence launch, and then ends.

let disposeBag = DisposeBag()    Observable.of(1,2,3,4,5).toArray().subscribe(onNext: {print($0)}).disposed(by: disposeBag)

Operation Result:

[1, 2, 3, 4, 5]

Reduce

Using an initial value and an operator, Observable all elements in the sequence are accumulated and converted into a single event signal. (PS: And map Some of the difference is: map to operate on a single element, reduce for all elements accumulated operations)

let disposeBag = DisposeBag()    Observable.of(1,10,100).reduce(1, accumulator: +).subscribe(onNext: {print($0)}).addDisposableTo(disposeBag)

Operation Result:

112

Concat

Observablemerges two sequences into a Observable sequence, and the Observable elements in another sequence are emitted when all elements of a sequence are successfully launched Observable .
Before the first Observable launch is complete, the second Observable emitted event is ignored, but it receives Observable Observable the last event of the second launch before the first one is completed.
Not a good idea, for example:

let disposeBag = DisposeBag()    let subject1 = BehaviorSubject(value: "??")let subject2 = BehaviorSubject(value: "??")    let variable = Variable(subject1)    variable.asObservable()    .concat()    .subscribe { print($0) }    .disposed(by: disposeBag)    subject1.onNext("??")subject1.onNext("??")    variable.value = subject2subject2.onNext("I would be ignored")subject2.onNext("??")    subject1.onCompleted()subject2.onNext("??")

Operation Result:

next(??)next(??)next(??)next(??)next(??)

Explanation: subject1 Before the launch completes the event

variable.value = subject2subject2.onNext("I would be ignored")subject2.onNext("??")

subject2The emitted events are ignored, but the subject2 last event of the launch is received, and therefore printed onnext(??) .

Thanks

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

RxSwift Series (vi)