RxSwift入坑记-各种概念解读
ShaFlinchum
8年前
<p>相信大家很早就听说过函数式响应编程概念，我是去年面试的时候接触到函数式响应编程的，当时也是第一次接触到MVVM这个概念，转眼都一年过去了，我却没有在函数式编程上做深入的研究，说来还真是惭愧。</p> <p>不过最近由于想要使用RxSwift，所以趁这个时候好好接触和研究一下传说中的函数式编程，由于网上关于RxSwift的教程资料很少，这篇文章其实就是最RxSwift官方文档和一些概念做一些解读。算是大家学习的参考文章吧！ 先挖个坑，这可能会是一个RxSwift系列，希望大家在学习的时候有所参考。</p> <h2><strong>RxSwift是什么</strong></h2> <p>RxSwif是 ReactiveX 的Swift版本，也就是一个函数式响应编程的框架。对，就这一句话。想要知道他做什么的，我们先来了解一下观察者模式。</p> <h2>观察者模式</h2> <p>关于观察者模式我想大伙应该都很了解了吧，什么KVO，通知等都是观察者模式，在设计模式中他可是一个重中之重的设计模式啊！比如一个宝宝在睡觉，爸爸妈妈，爷爷奶奶总不能在那边一只看着吧？那样子太累了。他们该做啥事就做啥事呗，只要听到宝宝的哭声，他们就给宝宝喂奶就行了。这就是一个典型的观察者模式。宝宝是被观察者，爸爸妈妈等是观察者也称作订阅者，只要被观察者发出了某些事件比如宝宝哭声、叫声都是一个事件，通知到订阅者，订阅者们就可以做相应的处理工作。哈哈，观察者模式很简单吧？</p> <h2><strong>RxSwift做了什么</strong></h2> <p>RxSwift把我们程序中每一个操作都看成一个事件，比如一个TextField中的文本改变，一个按钮被点击，或者一个网络请求结束等，每一个事件源就可以看成一个管道，也就是sequence，比如TextField，当我们改变里面的文本的时候，这个TextField就会不断的发出事件，从他的这个sequence中不断的流出，我们只需要监听这个sequence，每流出一个事件就做相应的处理。同理，Button也是一个sequence，每点击一次就流出一个事件。也就是我们把每一步都想成是一个事件就好去理解RxSwift了。看下图是不是很好理解了？</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/258aaed7921e7a56670957733cbd48e0.jpg"></p> <h2><strong>Observable和Observer</strong></h2> <p>理解了观察者模式这两个概念就很好理解了，Observable就是可被观察的，也就是我们说的宝宝，他也是事件源。而Observer就是我们的观察者，也就是当收到事件的时候去做某些处理的爸爸妈妈。观察者需要去订阅(subscribe)被观察者，才能收到Observable的事件通知消息。</p> <p>下面开始一些基本概念解读，通读一遍你会对RxSwift有非常深刻的认识了，其实也就是对整理了一下官方文档和加上自己的一些理解</p> <h2><strong>创建和订阅被观察者</strong></h2> <p>下面创建被观察者其实就是创建一个Obserable的sequence，就是创建一个流，然后就可以被订阅subscribe，这样被观察者发出时间消失，我们就能做相应的处理</p> <h3><strong>DisposeBag</strong></h3> <p>DisposeBag其实就相当于iOS中的ARC似得，会在适当的时候销毁观察者，相当于内存管理者吧。</p> <h3><strong>subscribe</strong></h3> <p>subscribe是订阅sequence发出的事件，比如next事件，error事件等。而subscribe(onNext:)是监听sequence发出的next事件中的element进行处理，他会忽略error和completed事件。相对应的还有subscribe(onError:) 和 subscribe(onCompleted:)</p> <h3><strong>never</strong></h3> <p>never就是创建一个sequence，但是不发出任何事件信号。</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/a2c9591c2c91614a0c26704afbce6f41.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() letneverSequence =Observable<String>.never() letneverSequenceSubscription = neverSequence .subscribe { _in print("This will never be printed") }.addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">结果是什么都不打印 </code></pre> <h3><strong>empty</strong></h3> <p>empty就是创建一个空的sequence,只能发出一个completed事件</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/c02585d921bb7c029aaa979419ef438b.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable<Int>.empty() .subscribe { event in print(event) } .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">completed </code></pre> <h3><strong>just</strong></h3> <p>just是创建一个sequence只能发出一种特定的事件，能正常结束</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/8476874f0a288e947d2f08158dd6faca.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.just("") .subscribe { event in print(event) } .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">next() completed </code></pre> <h3><strong>of</strong></h3> <p>of是创建一个sequence能发出很多种事件信号</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of("","","","") .subscribe(onNext: { element in print(element) }) .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift"> </code></pre> <p>如果把上面的onNext:去掉的话，结果会是这样子，也正好对应了我们subscribe中，subscribe只监听事件。</p> <pre> <code class="language-swift">next() next() next() next() completed </code></pre> <h3><strong>from</strong></h3> <p>from就是从集合中创建sequence，例如数组，字典或者Set</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.from(["","","",""]) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <h3><strong>create</strong></h3> <p>我们也可以自定义可观察的sequence，那就是使用create</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/710977506ff157aff223427240d9337a.jpg"></p> <p>create操作符传入一个观察者observer，然后调用observer的onNext，onCompleted和onError方法。返回一个可观察的obserable序列。</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() letmyJust = { (element:String) ->Observable<String>in returnObservable.create { observerin observer.on(.next(element)) observer.on(.completed) returnDisposables.create() } } myJust("") .subscribe { print($0) } .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">next() completed </code></pre> <h3><strong>range</strong></h3> <p>range就是创建一个sequence，他会发出这个范围中的从开始到结束的所有事件</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/3cc9a076125952c800b7df48b9a96a80.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.range(start:1,count:10) .subscribe { print($0) } .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">next(1) next(2) next(3) next(4) next(5) next(6) next(7) next(8) next(9) next(10) completed </code></pre> <h3><strong>repeatElement</strong></h3> <p>创建一个sequence，发出特定的事件n次</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/fb97ba8c28f199f80a47e11e79dfe049.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.repeatElement("") .take(3) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift"> </code></pre> <h3><strong>generate</strong></h3> <p>generate是创建一个可观察sequence，当初始化的条件为true的时候，他就会发出所对应的事件</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.generate( initialState: 0, condition: { $0<3}, iterate: { $0+1} ) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <h3><strong>deferred</strong></h3> <p>deferred会为每一为订阅者observer创建一个新的可观察序列</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/ebca18ee3b866e80a4f56dfea99d431f.jpg"></p> <p>下面例子中每次进行subscribe的时候都会去创建一个新的deferredSequence，所以Emitting会打印两遍。</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() varcount=1 letdeferredSequence =Observable<String>.deferred { print("Creating\(count)") count+=1 returnObservable.create { observerin print("Emitting...") observer.onNext("") observer.onNext("") observer.onNext("") returnDisposables.create() } } deferredSequence .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) deferredSequence .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">Creating 1 Emitting... Creating 2 Emitting... </code></pre> <h3><strong>error</strong></h3> <p>创建一个可观察序列，但不发出任何正常的事件，只发出error事件并结束</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable<Int>.error(TestError.test) .subscribe { print($0) } .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">error(test) </code></pre> <h3><strong>doOn</strong></h3> <p>doOn我感觉就是在直接onNext处理时候，先执行某个方法，doOnNext( <em>:)方法就是在subscribe(onNext:)前调用，doOnCompleted(</em> :)就是在subscribe(onCompleted:)前面调用的。</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of("","","","") .do(onNext: {print("Intercepted:", $0) }, onError: {print("Intercepted error:", $0) }, onCompleted: {print("Completed") }) .subscribe(onNext: { print($0) },onCompleted: {print("结束") }) .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">Intercepted: Intercepted: Intercepted: Intercepted: Completed 结束 </code></pre> <h2><strong>学会使用Subjects</strong></h2> <p>Subjet是observable和Observer之间的桥梁，一个Subject既是一个Obserable也是一个Observer，他既可以发出事件，也可以监听事件。</p> <h3><strong>PublishSubject</strong></h3> <p>当你订阅PublishSubject的时候，你只能接收到订阅他之后发生的事件。subject.onNext()发出onNext事件，对应的还有onError()和onCompleted()事件</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/a9fa3aac990705c7c1d9344fa7086135.jpg"></p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let subject = PublishSubject<String>() subject.addObserver("1").addDisposableTo(disposeBag) subject.onNext("") subject.onNext("") subject.addObserver("2").addDisposableTo(disposeBag) subject.onNext("️") subject.onNext("️") </code></pre> <pre> <code class="language-swift">Subscription: 1 Event: next() Subscription: 1 Event: next() Subscription: 1 Event: next(️) Subscription: 2 Event: next(️) Subscription: 1 Event: next(️) Subscription: 2 Event: next(️) </code></pre> <h3><strong>ReplaySubject</strong></h3> <p>当你订阅ReplaySubject的时候，你可以接收到订阅他之后的事件，但也可以接受订阅他之前发出的事件，接受几个事件取决与bufferSize的大小</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/52a2be702a80510b6c9d0cce6e1b72d4.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() letsubject =ReplaySubject<String>.create(bufferSize:1) subject.addObserver("1").addDisposableTo(disposeBag) subject.onNext("") subject.onNext("") subject.addObserver("2").addDisposableTo(disposeBag) subject.onNext("️") subject.onNext("️") </code></pre> <pre> <code class="language-swift">Subscription: 1 Event: next() Subscription: 1 Event: next() Subscription: 2 Event: next() //订阅之后还可以接受一次前面发出的事件 Subscription: 1 Event: next(️) Subscription: 2 Event: next(️) Subscription: 1 Event: next(️) Subscription: 2 Event: next(️) </code></pre> <h3><strong>BehaviorSubject</strong></h3> <p>当你订阅了BehaviorSubject，你会接受到订阅之前的最后一个事件。</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/1722e606b0df8b5bc6b3ad534b89a2f0.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() letsubject =BehaviorSubject(value:"") subject.addObserver("1").addDisposableTo(disposeBag) subject.onNext("") subject.onNext("") subject.addObserver("2").addDisposableTo(disposeBag) subject.onNext("️") subject.onNext("️") subject.addObserver("3").addDisposableTo(disposeBag) subject.onNext("") subject.onNext("") </code></pre> <pre> <code class="language-swift">Subscription: 1 Event: next() Subscription: 1 Event: next() Subscription: 1 Event: next() Subscription: 2 Event: next() //订阅之前的最后一个事件 Subscription: 1 Event: next(️) Subscription: 2 Event: next(️) Subscription: 1 Event: next(️) Subscription: 2 Event: next(️) Subscription: 3 Event: next(️) //订阅之前的最后一个事件 Subscription: 1 Event: next() Subscription: 3 Event: next() Subscription: 2 Event: next() Subscription: 1 Event: next() Subscription: 3 Event: next() Subscription: 2 Event: next() </code></pre> <p>PublishSubject, ReplaySubject和BehaviorSubject是不会自动发出completed事件的。</p> <h3><strong>Variable</strong></h3> <p>Variable是BehaviorSubject一个包装箱，就像是一个箱子一样，使用的时候需要调用asObservable()拆箱，里面的value是一个BehaviorSubject，他不会发出error事件，但是会自动发出completed事件。</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() letvariable =Variable("") variable.asObservable().addObserver("1").addDisposableTo(disposeBag) variable.value = "" variable.value = "" variable.asObservable().addObserver("2").addDisposableTo(disposeBag) variable.value = "️" variable.value = "️" </code></pre> <pre> <code class="language-swift">Subscription: 1 Event: next() Subscription: 1 Event: next() Subscription: 1 Event: next() Subscription: 2 Event: next() Subscription: 1 Event: next(️) Subscription: 2 Event: next(️) Subscription: 1 Event: next(️) Subscription: 2 Event: next(️) Subscription: 1 Event: completed Subscription: 2 Event: completed </code></pre> <h2><strong>联合操作</strong></h2> <p>联合操作就是把多个Observable流合成单个Observable流</p> <h3><strong>startWith</strong></h3> <p>在发出事件消息之前，先发出某个特定的事件消息。比如发出事件2 ，3然后我startWith(1)，那么就会先发出1，然后2 ，3.</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/54332de646ea7cf6f0d653c55b215f08.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of("2","3") .startWith("1") .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <h3><strong>merge</strong></h3> <p>合并两个Observable流合成单个Observable流，根据时间轴发出对应的事件</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/3dc93adebee7e1eaa8d634d324fe2e23.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() letsubject1 =PublishSubject<String>() letsubject2 =PublishSubject<String>() Observable.of(subject1, subject2) .merge() .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) subject1.onNext("️") subject1.onNext("️") subject2.onNext("①") subject2.onNext("②") subject1.onNext("") subject2.onNext("③") </code></pre> <pre> <code class="language-swift">️ ️ ① ② ③ </code></pre> <h3><strong>zip</strong></h3> <p>绑定超过最多不超过8个的Observable流，结合在一起处理。注意Zip是一个事件对应另一个流一个事件。</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/e1e7381002ed2b8f0b6ee6a9ee97f5c3.jpg"></p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let stringSubject = PublishSubject<String>() let intSubject = PublishSubject<Int>() Observable.zip(stringSubject, intSubject) { stringElement, intElement in "\(stringElement) \(intElement)" } .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) stringSubject.onNext("️") stringSubject.onNext("️") intSubject.onNext(1) intSubject.onNext(2) stringSubject.onNext("") intSubject.onNext(3) </code></pre> <pre> <code class="language-swift">️ 1 将stringSubject和intSubject压缩到一起共同处理 ️ 2 3 </code></pre> <h3><strong>combineLatest</strong></h3> <p>绑定超过最多不超过8个的Observable流，结合在一起处理。和Zip不同的是combineLatest是一个流的事件对应另一个流的最新的事件，两个事件都会是最新的事件，可将下图与Zip的图进行对比。</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/e7572078c27af54f52362fb625835d96.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() letstringSubject =PublishSubject<String>() letintSubject =PublishSubject<Int>() Observable.combineLatest(stringSubject, intSubject) { stringElement, intElementin "\(stringElement)\(intElement)" } .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) stringSubject.onNext("️") stringSubject.onNext("️") intSubject.onNext(1) intSubject.onNext(2) stringSubject.onNext("") </code></pre> <pre> <code class="language-swift">️ 1 ️ 2 2 </code></pre> <h3><strong>switchLatest</strong></h3> <p>switchLatest可以对事件流进行转换，本来监听的subject1，我可以通过更改variable里面的value更换事件源。变成监听subject2了</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/aa64c5f1f3720eb402f45ee8aa6cffb4.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() letsubject1 =BehaviorSubject(value:"⚽️") letsubject2 =BehaviorSubject(value:"") letvariable =Variable(subject1) variable.asObservable() .switchLatest() .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) subject1.onNext("") subject1.onNext("") variable.value = subject2 subject1.onNext("⚾️") subject2.onNext("") variable.value = subject1 subject2.onNext("田腾飞") subject1.onNext("沸腾天") </code></pre> <pre> <code class="language-swift">⚽️ ⚾️ 沸腾天 </code></pre> <h2><strong>变换操作</strong></h2> <h3>map</h3> <p>通过传入一个函数闭包把原来的sequence转变为一个新的sequence的操作</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/0a18fa2143cb0c241046fc22d07d329a.jpg"></p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of(1,2,3) .map{ $0* $0} .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">1 每一个元素自己相乘 4 9 </code></pre> <h3><strong>flatMap</strong></h3> <p>将一个sequence转换为一个sequences，当你接收一个sequence的事件，你还想接收其他sequence发出的事件的话可以使用flatMap，她会将每一个sequence事件进行处理以后，然后再以一个sequence形式发出事件。而且flatMap有一次拆包动作，请看代码解析。</p> <p style="text-align: center;"><img src="https://simg.open-open.com/show/c3f0ad71dcdc8698980473cbf60e49f6.jpg"></p> <pre> <code class="language-swift">let disposeBag = DisposeBag() struct Player { var score: Variable<Int> //里面是一个Variable } let = Player(score: Variable(80)) let = Player(score: Variable(90)) let = Player(score: Variable(550)) let player = Variable() //将player转为Variable player.asObservable() //拆箱转成可被监听的sequence .flatMap { $0.score.asObservable() } // flatMap有一次拆包动作，$0本来应该是一个BehaviorSubject类型，但是直接访问了score。所以猜想flatMap对behaviorSubject进行了onNext拆包取数据 .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) .score.value = 85 player.value = //更换了value，相当于又添加了一个sequence，两个sequence都可以接收 .score.value = 95 .score.value = 222 player.value = .score.value = 100 </code></pre> <h3><strong>flatMapLatest</strong></h3> <p>flatMapLatest只会接收最新的value事件，将上例改为flatMapLatest。结果为</p> <h3>scan</h3> <p>scan就是给一个初始化的数，然后不断的拿前一个结果和最新的值进行处理操作。</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of(10,100,1000) .scan(1) { aggregateValue, newValuein aggregateValue + newValue } .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <h2><strong>过滤和约束</strong></h2> <h3><strong>filter</strong></h3> <p>filter很好理解，就是过滤掉某些不符合要求的事件</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of( "","","", "","","", "","","") .filter{ $0=="" } .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift"> </code></pre> <h3><strong>distinctUntilChanged</strong></h3> <p>distinctUntilChanged就是当下一个事件与前一个事件是不同事件的事件才进行处理操作</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of("","","","","","","") .distinctUntilChanged() .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift"> </code></pre> <h3><strong>elementAt</strong></h3> <p>只处理在指定位置的事件</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of("","","","","","") .elementAt(3) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <p></p> <h3><strong>single</strong></h3> <p>找出在sequence只发出一次的事件，如果超过一个就会发出error错误</p> <pre> <code class="language-swift">Observable.of("","","","","","") .single() .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift"> //单一信号超过了一个 Received unhandled error: /var/folders/hz/v15ld5mj0nqf83d21j13y0tw0000gn/T/./lldb/7229/playground107.swift:69:__lldb_expr_107 -> Sequence contains more than one element. </code></pre> <pre> <code class="language-swift">Observable.of("","","","","","") .single { $0==""}//青蛙只有一个，completed .subscribe { print($0) } .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">Observable.of("", "", "", "", "", "") .single { $0 == "" } //兔子有两个，会发出error .subscribe { print($0) } .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">Observable.of("", "", "", "", "", "") .single { $0 == "" } //没有蓝色球，会发出error .subscribe { print($0) } .addDisposableTo(disposeBag) </code></pre> <h3><strong>take</strong></h3> <p>只处理前几个事件信号,</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of("","","","","","") .take(3) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift"> </code></pre> <h3><strong>takeLast</strong></h3> <p>只处理后几个事件信号</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of("","","","","","") .takeLast(3) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift"> </code></pre> <h3><strong>takeWhile</strong></h3> <p>当条件满足的时候进行处理</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of(1,2,3,4,5,6) .takeWhile { $0<4} .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <h3><strong>takeUntil</strong></h3> <p>接收事件消息，直到另一个sequence发出事件消息的时候。</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let sourceSequence = PublishSubject<String>() let referenceSequence = PublishSubject<String>() sourceSequence .takeUntil(referenceSequence) .subscribe { print($0) } .addDisposableTo(disposeBag) sourceSequence.onNext("") sourceSequence.onNext("") sourceSequence.onNext("") referenceSequence.onNext("") //停止接收消息 sourceSequence.onNext("") sourceSequence.onNext("") sourceSequence.onNext("") </code></pre> <pre> <code class="language-swift">next() next() next() completed </code></pre> <h3><strong>skip</strong></h3> <p>取消前几个事件</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of("","","","","","") .skip(2) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift"> </code></pre> <h3><strong>skipWhile</strong></h3> <p>满足条件的事件消息都取消</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() Observable.of(1,2,3,4,5,6) .skipWhile { $0<4} .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <h3><strong>skipWhileWithIndex</strong></h3> <p>满足条件的都被取消，传入的闭包同skipWhile有点区别而已</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.of("", "", "", "", "", "") .skipWhileWithIndex { element, index in index < 3 } .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <h3><strong>skipUntil</strong></h3> <p>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</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let sourceSequence = PublishSubject<String>() let referenceSequence = PublishSubject<String>() sourceSequence .skipUntil(referenceSequence) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) sourceSequence.onNext("") sourceSequence.onNext("") sourceSequence.onNext("") referenceSequence.onNext("") sourceSequence.onNext("") sourceSequence.onNext("") sourceSequence.onNext("") } </code></pre> <h2><strong>数学操作</strong></h2> <h3><strong>toArray</strong></h3> <p>将sequence转换成一个array，并转换成单一事件信号，然后结束</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.range(start: 1, count: 10) .toArray() .subscribe { print($0) } .addDisposableTo(disposeBag) </code></pre> <pre> <code class="language-swift">next([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) completed </code></pre> <h3><strong>reduce</strong></h3> <p>用一个初始值，对事件数据进行累计操作。reduce接受一个初始值，和一个操作符号</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.of(10, 100, 1000) .reduce(1, accumulator: +) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <h3><strong>concat</strong></h3> <p>concat会把多个sequence和并为一个sequence，并且当前面一个sequence发出了completed事件，才会开始下一个sequence的事件。</p> <p>在第一sequence完成之前，第二个sequence发出的事件都会被忽略，但会接收一完成之前的二发出的最后一个事件。不好解释，看例子说明</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let subject1 = BehaviorSubject(value: "") let subject2 = BehaviorSubject(value: "") let variable = Variable(subject1) variable.asObservable() .concat() .subscribe { print($0) } .addDisposableTo(disposeBag) subject1.onNext("") subject1.onNext("") variable.value = subject2 subject2.onNext("") //1完成前，会被忽略 subject2.onNext("teng") //1完成前，会被忽略 subject2.onNext("fei") //1完成前的最后一个，会被接收 subject1.onCompleted() subject2.onNext("") </code></pre> <pre> <code class="language-swift">next() next() next() next(fei) next() </code></pre> <h2><strong>连接性操作</strong></h2> <p>Connectable Observable有订阅时不开始发射事件消息，而是仅当调用它们的connect（）方法时。这样就可以等待所有我们想要的订阅者都已经订阅了以后，再开始发出事件消息，这样能保证我们想要的所有订阅者都能接收到事件消息。其实也就是等大家都就位以后，开始发出消息。</p> <h3><strong>publish</strong></h3> <p>将一个正常的sequence转换成一个connectable sequence</p> <pre> <code class="language-swift">let intSequence = Observable<Int>.interval(1, scheduler: MainScheduler.instance) .publish() _ = intSequence .subscribe(onNext: { print("Subscription 1:, Event: \($0)") }) delay(2) { _ = intSequence.connect() } //相当于把事件消息推迟了两秒 delay(4) { _ = intSequence .subscribe(onNext: { print("Subscription 2:, Event: \($0)") }) } delay(6) { _ = intSequence .subscribe(onNext: { print("Subscription 3:, Event: \($0)") }) } </code></pre> <pre> <code class="language-swift">Subscription 1:, Event: 0 Subscription 1:, Event: 1 Subscription 2:, Event: 1 Subscription 1:, Event: 2 Subscription 2:, Event: 2 Subscription 1:, Event: 3 Subscription 3:, Event: 3 Subscription 2:, Event: 3 Subscription 1:, Event: 4 Subscription 3:, Event: 4 </code></pre> <h3><strong>replay</strong></h3> <p>将一个正常的sequence转换成一个connectable sequence，然后和replaySubject相似，能接收到订阅之前的事件消息。</p> <pre> <code class="language-swift">let intSequence = Observable<Int>.interval(1, scheduler: MainScheduler.instance) .replay(5) //接收到订阅之前的5条事件消息 _ = intSequence .subscribe(onNext: { print("Subscription 1:, Event: \($0)") }) delay(2) { _ = intSequence.connect() } delay(4) { _ = intSequence .subscribe(onNext: { print("Subscription 2:, Event: \($0)") }) } delay(8) { _ = intSequence .subscribe(onNext: { print("Subscription 3:, Event: \($0)") }) } </code></pre> <h3><strong>multicast</strong></h3> <p>将一个正常的sequence转换成一个connectable sequence，并且通过特性的subject发送出去，比如PublishSubject，或者replaySubject，behaviorSubject等。不同的Subject会有不同的结果。</p> <pre> <code class="language-swift">let subject = PublishSubject<Int>() _ = subject .subscribe(onNext: { print("Subject: \($0)") }) let intSequence = Observable<Int>.interval(1, scheduler: MainScheduler.instance) .multicast(subject) _ = intSequence .subscribe(onNext: { print("\tSubscription 1:, Event: \($0)") }) delay(2) { _ = intSequence.connect() } delay(4) { _ = intSequence .subscribe(onNext: { print("\tSubscription 2:, Event: \($0)") }) } </code></pre> <h2><strong>错误处理</strong></h2> <h3>catchErrorJustReturn</h3> <p>遇到error事件的时候，就return一个值，然后结束</p> <pre> <code class="language-swift">letdisposeBag =DisposeBag() letsequenceThatFails =PublishSubject<String>() sequenceThatFails .catchErrorJustReturn("") .subscribe { print($0) } .addDisposableTo(disposeBag) sequenceThatFails.onNext("") sequenceThatFails.onNext("") sequenceThatFails.onNext("") sequenceThatFails.onNext("") sequenceThatFails.onError(TestError.test) </code></pre> <pre> <code class="language-swift">next() next() next() next() next() completed </code></pre> <h3><strong>catchError</strong></h3> <p>捕获error进行处理，可以返回另一个sequence进行订阅</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let sequenceThatFails = PublishSubject<String>() let recoverySequence = PublishSubject<String>() sequenceThatFails .catchError { print("Error:", $0) return recoverySequence } .subscribe { print($0) } .addDisposableTo(disposeBag) sequenceThatFails.onNext("") sequenceThatFails.onNext("") sequenceThatFails.onNext("") sequenceThatFails.onNext("") sequenceThatFails.onError(TestError.test) recoverySequence.onNext("") </code></pre> <pre> <code class="language-swift">next() next() next() next() Error: test next() </code></pre> <h3><strong>retry</strong></h3> <p>遇见error事件可以进行重试，比如网络请求失败，可以进行重新连接</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() var count = 1 let sequenceThatErrors = Observable<String>.create { observer in observer.onNext("") observer.onNext("") observer.onNext("") if count == 1 { observer.onError(TestError.test) print("Error encountered") count += 1 } observer.onNext("") observer.onNext("") observer.onNext("") observer.onCompleted() return Disposables.create() } sequenceThatErrors .retry(3) //不传入数字的话，只会重试一次 .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <h2><strong>debug</strong></h2> <h3><strong>debug</strong></h3> <p>打印所有的订阅, 事件和disposals</p> <pre> <code class="language-swift">sequenceThatErrors .retry(3) .debug() .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) </code></pre> <h3><strong>RxSwift.Resources.total</strong></h3> <p>查看RxSwift所有资源的占用</p> <pre> <code class="language-swift">print(RxSwift.Resources.total) </code></pre> <p>啊，文章终于结束，这篇文章比较长，基本上涵盖了官方文档所有的概念，其中不免有些错误与疏漏，希望能在你学习RxSwift的时候能有一些参考价值吧！！！</p> <p> </p> <p>来自：http://www.codertian.com/2016/11/27/RxSwift-ru-keng-ji-read-document/</p> <p> </p>