RxSwift Creating Observables

除非有订阅者，否则Observable不会执行它们的闭包。

• Create

创建一个自定义的Observable序列

image.png

let disposeBag = DisposeBag()
let myjust = { (element: String) -> Observable<String> in
    return Observable.create{ observer in
        observer.on(.next(element))
        observer.on(.completed)
        return Disposables.create()
    }
}

myjust("篮球").subscribe({ (element) in
    print(element)
}).disposed(by: disposeBag)

• generate

let source = Observable.generate(
   initialState: 0,
   condition: { $0 < 3 },
   iterate: { $0 + 1 }
)

source.subscribe {
   print($0)
}

next(0)
next(1)
next(2)
completed

• deferred

  为每一个订阅者创建一个新的Observable序列。

let disposeBag = DisposeBag()
var count = 1
let defferedSequen = Observable<String>.deferred {
    print("count = \(count)")
    count += 1

    return Observable.create({ (observer) -> Disposable in
        observer.onNext("山羊")
        observer.onNext("野猪")
        observer.onNext("小猫")

        return Disposables.create()
    })
}

defferedSequen.subscribe(onNext: {
    print($0)
}).disposed(by: disposeBag)
defferedSequen.subscribe(onNext: {
    print($0)
}).disposed(by: disposeBag)

• empty

创建一个只发送completed事件的空Observable序列。

image.png

let disposeBag = DisposeBag()
Observable<Int>.empty().subscribe({ (event) in
    print(event)
}).disposed(by: disposeBag)

• never

创建一个永不终止且不发出任何事件的序列。

let disposeBag = DisposeBag()
Observable<String>.never().subscribe({ (_) in
    print("this will never be printed")
}).disposed(by: disposeBag)

• of、from

image.png

1. of
   创建一个固定数量元素的Observable序列。

let disposeBag = DisposeBag()
Observable.of("元素1","元素2","元素3","元素4","元素5").subscribe(onNext: { (element) in
    print(element)
}).disposed(by: disposeBag)

2. from
   从一个序列(如Array/Dictionary/Set)中创建一个Observable序列。

//从一个序列(如Array/Dictionary/Set)中创建一个Observable序列。

let disposeBag = DisposeBag()
Observable.from(["元素1","元素2","元素3","元素4","元素5"]).subscribe(onNext: {
    print($0)
}).disposed(by: disposeBag)

• Interval

创建一个可观察对象，该对象发出以给定时间间隔为间隔的整数序列

image.png

Observable<Int>.interval(.seconds(1), scheduler: MainScheduler.asyncInstance)
                    .subscribe{print($0)}
                    .disposed(by: disposeBag)
// next(0)
// next(1)
// next(2)
// next(3)
// next(4)

• just

创建一个只有一个元素的Observable序列。

image.png

let source = Observable.just(1, 2, 3)

source.subscribe {
    print($0)
}

let source2 = Observable.just([1,2,3])

source2.subscribe {
    print($0)
}

next((1, 2, 3))
completed
next([1, 2, 3])
completed

• range

创建一个Observable序列，它会发出一系列连续的整数，然后终止。

image.png

let disposeBag = DisposeBag()
Observable.range(start: 1, count: 10).subscribe {
    print($0) 
}.disposed(by: disposeBag)

• repeatElement

创建一个Observable序列，它可以无限地释放给定元素。

let disposeBag = DisposeBag()
Observable.repeatElement("🏀").take(3).subscribe(onNext: {
    print($0)
})

• timer

dueTime： 延时
period： 间隔时间

let seq = Observable<Int>.timer(.seconds(2), period: .seconds(1), scheduler: MainScheduler.asyncInstance)
print("订阅 time:", Date())
seq.subscribe{print("收到事件:",$0,"time:",Date())}
    .disposed(by: disposeBag)

订阅 time: 2018-03-23 03:06:49 +0000
收到事件: next(0) time: 2018-03-23 03:06:51 +0000
收到事件: next(1) time: 2018-03-23 03:06:52 +0000
收到事件: next(2) time: 2018-03-23 03:06:53 +0000
收到事件: next(3) time: 2018-03-23 03:06:54 +0000
收到事件: next(4) time: 2018-03-23 03:06:55 +0000
收到事件: next(5) time: 2018-03-23 03:06:56 +0000
收到事件: next(6) time: 2018-03-23 03:06:57 +0000
............

• error

创建一个不会发送任何条目并且立即终止错误的Observable序列。

  let disposeBag = DisposeBag()
  Observable<Int>.error(NSError()).subscribe { (err) in
            print(err)
        }.disposed(by: disposeBag)