distinctUntilChanged

過濾連續重複的事件

let ob = Observable.of(1, 1, 1, 3, 5, 7, 9, 9)
ob.distinctUntilChanged().subscribe(onNext: { element in
    print(element)
//1 3 5 7 9
}).disposed(by: disposeBag)

single

只發送一次正常事件，如果沒有或者超過 1 個會發送 error 事件

let ob = Observable.of(1,2)
ob.single().subscribe(onNext: { element in
    print(element)
}, onError: { error in
    print("錯誤",error)
}).disposed(by: disposeBag)
//        1
//        錯誤 Sequence contains more than one element.


//----- single 增加過濾
let ob = Observable.of(1, 2, 1)
ob.single { $0 == 2 }.subscribe(onNext: { element in
    print(element)
}, onError: { error in
    print("錯誤", error)
}).disposed(by: disposeBag)
//        2
 

elementAt

獲取指定位置的事件，0 開始。 如果沒有發生該指定位置事件 會發送錯誤

let ob = Observable.of(0, 1, 2, 3, 4)
ob.elementAt(2).subscribe(onNext: { element in
    print(element)
}, onError: { error in
    print(error)
}).disposed(by: disposeBag)
//2

ignoreElements

會忽略所有主動傳送的event事件，只保留 error 事件和 Completed事件

let ob = Observable.of(0,1,2,3,4)
ob.ignoreElements().subscribe {
    print("Completed")
} onError: { (error) in
    print(error)
}.disposed(by: disposeBag)
 

take

只取前 n 個事件，數量達到或不足會發送 Completed。

let ob = Observable.of(0, 1, 2, 3)
ob.take(2).subscribe { element in
    print(element)
} onError: { error in
    print(error)
} onCompleted: {
    print("onCompleted")
}.disposed(by: disposeBag)

takeLast

只取後 n 個事件，數量達到或不足會發送 Completed。

let ob = Observable.of(0, 1, 2, 3, 4)
ob.takeLast(12).subscribe { element in
    print(element)
} onError: { error in
    print(error)
} onCompleted: {
    print("onCompleted")
}.disposed(by: disposeBag)
 

skip

跳過前 n 個事件，傳送完剩下的事件後會傳送onCompleted。不足 n 個直接傳送onCompleted。

let ob = Observable.of(0,1,2,3,4,5)
ob.skip(4).subscribe { (element) in
    print(element)
} onError: { (error) in
    print(error)
} onCompleted: {
    print("onCompleted")
}.disposed(by: disposeBag)

debounce

當兩個事件的傳送間隔大於約定時間時才會收到該事件，常用的例子是搜尋時延遲搜尋

let ob = PublishSubject<String>()
ob.debounce(RxTimeInterval.seconds(1), scheduler: MainScheduler.instance).subscribe(onNext: { element in
    print("收", element, CFAbsoluteTimeGetCurrent())
}).disposed(by: disposeBag)
print("發", "aaa", CFAbsoluteTimeGetCurrent())
ob.onNext("aaa")
DispatchQueue.global().asyncAfter(deadline: .now() + 0.5) {
    print("發", "bbb", CFAbsoluteTimeGetCurrent())
    ob.onNext("bbb")
}
DispatchQueue.global().asyncAfter(deadline: .now() + 1.5) {
    print("發", "ccc", CFAbsoluteTimeGetCurrent())
    ob.onNext("ccc")
}
DispatchQueue.global().asyncAfter(deadline: .now() + 3.5) {
    print("發", "ddd", CFAbsoluteTimeGetCurrent())
    ob.onNext("ddd")
}

//發 aaa 627481044.719082
//發 bbb 627481045.241852
//發 ccc 627481046.231139
//收 ccc 627481047.233378
//發 ddd 627481048.552644
//收 ddd 627481049.55595

搬遷自本人簡書