takeUntil

忽略掉在第二个 Observable 产生事件后发出的那部分元素

takeUntil 操作符将镜像源 Observable，它同时观测第二个 Observable。一旦第二个 Observable 发出一个元素或者产生一个终止事件，那个镜像的 Observable 将立即终止。

演示

let disposeBag = DisposeBag()

let sourceSequence = PublishSubject<String>()
let referenceSequence = PublishSubject<String>()

sourceSequence
    .takeUntil(referenceSequence)
    .subscribe { print($0) }
    .disposed(by: disposeBag)

sourceSequence.onNext("🐱")
sourceSequence.onNext("🐰")
sourceSequence.onNext("🐶")

referenceSequence.onNext("🔴")

sourceSequence.onNext("🐸")
sourceSequence.onNext("🐷")
sourceSequence.onNext("🐵")

输出结果：

next(🐱)
next(🐰)
next(🐶)
completed