RxSwift_v1.0笔记——5 Filtering Operators

Skipping operators

ignoreElements

next不通过，.completed or .error通过

ignore .next event elements. It will, however, allow through stop events, i.e.,

.completed or .error events.

example(of: "ignoreElements") {

  // 1
  let strikes = PublishSubject()

  let disposeBag = DisposeBag()

  // 2
  strikes
    .ignoreElements()
    .subscribe { _ in
      print("You're out!")
    }
    .addDisposableTo(disposeBag)

  strikes.onNext("X")
  strikes.onNext("X")
  strikes.onNext("X")
  strikes.onCompleted()
}
--- Example of: ignoreElements ---
You're out!

elementAt

只处理在指定位置的事件

example(of: "elementAt") {

  // 1
  let strikes = PublishSubject()

  let disposeBag = DisposeBag()

  //  2
  strikes
    .elementAt(2)
    .subscribe(onNext: { _ in
      print("You're out!")
    })
    .addDisposableTo(disposeBag)

  strikes.onNext("X")
  strikes.onNext("X")
  strikes.onNext("X")

}
--- Example of: elementAt ---
You're out!

filter

过滤掉某些不符合要求的事件

example(of: "filter") {

  let disposeBag = DisposeBag()

  // 1
  Observable.of(1, 2, 3, 4, 5, 6)
    // 2
    .filter { integer in
      integer % 2 == 0
    }
    // 3
    .subscribe(onNext: {
      print($0)
    })
    .addDisposableTo(disposeBag)

}
--- Example of: filter ---
2
4
6

Skipping operators

skip

取消前几个事件

example(of: "skip") {
  let disposeBag = DisposeBag()

  // 1
  Observable.of("A", "B", "C", "D", "E", "F")
    // 2
    .skip(3)
    .subscribe(onNext: {
      print($0)
    })
    .addDisposableTo(disposeBag)
}
--- Example of: skip ---
D
E
F

skipWhile

从开始，满足条件的事件消息都取消，直到不满足时之后的都通过

example(of: "skipWhile") {
  let disposeBag = DisposeBag()

  // 1
  Observable.of(2, 2, 3, 4, 4)
    // 2
    .skipWhile { integer in
      integer % 2 == 0
    }
    .subscribe(onNext: {
      print($0)
    })
    .addDisposableTo(disposeBag)
}
--- Example of: skipWhile ---
3
4
4

skipUntil

直到某个sequence发出了事件消息，才开始接收当前sequence发出的事件消息

example(of: "skipUntil") {

  let disposeBag = DisposeBag()

  // 1
  let subject = PublishSubject()
  let trigger = PublishSubject()

  // 2
  subject
    .skipUntil(trigger)
    .subscribe(onNext: {
      print($0)
    })
    .addDisposableTo(disposeBag)

  subject.onNext("A")
  subject.onNext("B")

  trigger.onNext("X")
  subject.onNext("C")
}
--- Example of: skipUntil ---
C

Taking operators

take

只处理前几个事件信号

example(of: "take") {

  let disposeBag = DisposeBag()

  // 1
  Observable.of(1, 2, 3, 4, 5, 6)
    // 2
    .take(3)
    .subscribe(onNext: {
      print($0)
    })
    .addDisposableTo(disposeBag)
}
--- Example of: take ---
1
2
3

takeWhileWithIndex

只要不满足条件就停止

example(of: "takeWhileWithIndex") {

  let disposeBag = DisposeBag()

  // 1
  Observable.of(2, 2, 4, 4, 6, 6)
    // 2
    .takeWhileWithIndex { integer, index in
      // 3
      integer % 2 == 0 && index < 3
    }
    // 4
    .subscribe(onNext: {
      print($0)
    })
    .addDisposableTo(disposeBag)
}
--- Example of: takeWhileWithIndex ---
2
2
4

takeUntil

接收事件消息，直到另一个sequence发出事件消息的时候就终止

example(of: "takeUntil") {

  let disposeBag = DisposeBag()

  // 1
  let subject = PublishSubject()
  let trigger = PublishSubject()

  // 2
  subject
    .takeUntil(trigger)
    .subscribe(onNext: {
      print($0)
    })
    .addDisposableTo(disposeBag)

  // 3
  subject.onNext("1")
  subject.onNext("2")

  trigger.onNext("X")

  subject.onNext("3")
}
--- Example of: takeUntil ---
1
2

Distinct operators

distinctUntilChanged

当下一个事件与前一个事件是不同的事件才进行处理操作

example(of: "distinctUntilChanged") {

  let disposeBag = DisposeBag()

  // 1
  Observable.of("A", "A", "B", "B", "A")
    // 2
    .distinctUntilChanged()
    .subscribe(onNext: {
      print($0)
    })
    .addDisposableTo(disposeBag)
}
--- Example of: distinctUntilChanged ---
A
B
A

example(of: "distinctUntilChanged(_:)") {

  let disposeBag = DisposeBag()

  // 1
  let formatter = NumberFormatter()
  formatter.numberStyle = .spellOut

  // 2
  Observable.of(10, 110, 20, 200, 210, 310)
    // 3
    .distinctUntilChanged { a, b in
      // 4
      guard let aWords = formatter.string(from: a)?.components(separatedBy: " "),
        let bWords = formatter.string(from: b)?.components(separatedBy: " ")
        else {
          return false
      }

      var containsMatch = false

      // 5
      for aWord in aWords {
        for bWord in bWords {
          if aWord == bWord {
            containsMatch = true
            break
          }
        }
      }

      return containsMatch
    }
    // 4
    .subscribe(onNext: {
      print($0)
    })
    .addDisposableTo(disposeBag)
}
--- Example of: distinctUntilChanged(_:) ---
10
20
200