1. startWith(value)

• 기존 리스트에 첫 번째 이벤트 추가

example(of: "Start with") {
    let numbers = Observable.of(2,3,4)
    
    let observable = numbers.startWith(100)
    observable.subscribe{
        print($0)
    }.disposed(by: disposeBag)
}
--- Example of:Start with---
next(100)
next(2)
next(3)
next(4)
completed

2. concat

2가지 옵저버블의 시퀀스를 합쳐줌

example(of: "Observerble.concet") {
    let first = Observable.of(1,2,3,4)
    let second = Observable.from([5,6,7])
    Observable.concat([first,second]).subscribe{
        print($0)
    }.disposed(by: disposeBag)
}
--- Example of:Observerble.concet---
next(1)
next(2)
next(3)
next(4)
next(5)
next(6)
next(7)
completed

3. merge

두 개의 Observalble Sequence를 하나의 Observable Sequence로 합침

example(of: "merge") {
    let left = PublishSubject<String>()
    let right = PublishSubject<String>()
    
    let source = Observable.of(left.asObserver(), right.asObserver())
    
    source.merge().subscribe{
        print($0)
    }
    
    var lValue = ["A","B","C"]
    var rValue = ["C","D","E"]
    
    repeat{
        switch Bool.random() {
        case true where !lValue.isEmpty:
            left.onNext("Left: " + lValue.removeFirst())
        case false where !rValue.isEmpty:
            right.onNext("RIGHT: " + rValue.removeFirst())
        default:
            break
        }
        
    }while !lValue.isEmpty || !rValue.isEmpty
    
    left.onCompleted()
    right.onCompleted()
}
--- Example of:merge---
next(RIGHT: C)
next(Left: A)
next(RIGHT: D)
next(Left: B)
next(Left: C)
next(RIGHT: E)
completed

4.combineLatest

• 하나의 이벤트만 저장 가능했던 Observable sequence를 여러개의 이벤트를 저장하게끔함.

• left를 기준으로 right가 나중에 나오면 모든 left에서의 최신 값과 매칭

  

  right의 이벤트가 emit될때 left의 최신 이벤트와 매칭해서 1개의 시퀀스를 생성해줌

  example(of: "combineLatest") {
      let left = PublishSubject<String>()
      let right = PublishSubject<String>()
      
      let observalbe = Observable.combineLatest(left, right) { leftElement, rightElement in
          "\\(leftElement) \\(rightElement)"
      }
      
      let disposable = observalbe.subscribe(onNext : {value in print(value)})
      
      print(">Sending a value to Left")
      left.onNext("hello,")
      print(">Sending a value to Left")
      left.onNext("hello???,")
      print(">Sending a value to right")
      right.onNext("world")
      print(">Sending another value to. right")
      right.onNext("RxSwift")
      print(">Sending another value to Left")
      left.onNext("Have a good day,")
      
      left.onCompleted()
      right.onCompleted()
      
      
  }
  --- Example of:combineLatest---
  >Sending a value to Left
  >Sending a value to Left
  >Sending a value to right
  hello???, world
  >Sending another value to. right
  hello???, RxSwift
  >Sending another value to Left
  Have a good day, RxSwift
  

5.Zip

• combineLatest와 최근의 이벤트들과 짝지어지지만, 갯수 제한이 생김

더적은 쪽의 이벤트의 개수에 맞게 짝지어서 연결해 줌

example(of: "ZIP") {
    enum Weather{
        case cloudy
        case rainny
        case sunny
    }
    let left : Observable<Weather> = Observable.of(.sunny,.cloudy,.rainny,.rainny,.cloudy,.cloudy)
    let right =  Observable.of("KOR","USA","CNA","JPN","TPA")
    let observalbe = Observable.zip(left, right) { weather, country in
        return "It's \\(weather) in \\(country)"
    }
    observalbe.subscribe(onNext:{
        print($0)
    })
}
--- Example of:ZIP---
It's sunny in KOR
It's cloudy in USA
It's rainny in CNA
It's rainny in JPN
It's cloudy in TPA