使用RxSwift Observables的递归调用

Question

我正在尝试使用RxSwift Observables进行递归调用。

import RxSwift

func observeUntil(initialValue: Int) -> Observable<Int> {

return Observable.deferred {
    .just(initialValue)
}
.do(onNext: {
    print("current item is", $0)
})
.flatMapLatest{ (item) -> Observable<Int> in
    if item < 5 {
        return Observable.just(item)
//                    .delay(.seconds(1), scheduler: MainScheduler.instance)
            .flatMapLatest{observeUntil(initialValue: $0 + 1)}
    } else {
        return .just(item)
    }
}
}
_ = observeUntil(initialValue: 0)
.subscribe()

当我在上面的代码中注释延迟时，输出如下所示正确显示

current item is 0
current item is 1
current item is 2
current item is 3
current item is 4
current item is 5
Program ended with exit code: 0

带延迟代码仅输出

current item is 0
Program ended with exit code: 0

[请帮助我了解添加延迟后会发生什么。

Answer 1

_ = observeUntil(initialValue: 0).subscribe()