RxSwift入坑解读-你所需要知道的各种概念
<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>RxSwift是什么</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>RxSwift做了什么</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> <p>sequence.png</p> <h2>Observable和Observer</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>创建和订阅被观察者</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>DisposeBag</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>subscribe</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>never</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> <p>never.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let neverSequence = Observable<String>.never() let neverSequenceSubscription = 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>empty</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> <p>empty.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable<Int>.empty() .subscribe { event in print(event) } .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">completed</code></pre> <h3>just</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> <p>just.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.just(":red_circle:") .subscribe { event in print(event) } .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">next(:red_circle:) completed</code></pre> <h3>of</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">let disposeBag = DisposeBag() Observable.of(":dog:", ":cat:", ":mouse:", ":hamster:") .subscribe(onNext: { element in print(element) }) .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">:dog: :cat: :mouse: :hamster:</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(:dog:) next(:cat:) next(:mouse:) next(:hamster:) completed</code></pre> <h3>from</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">let disposeBag = DisposeBag() Observable.from([":dog:", ":cat:", ":mouse:", ":hamster:"]) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <h3>create</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.png</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">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(":red_circle:") .subscribe { print($0) } .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">next(:red_circle:) completed</code></pre> <h3>range</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> <p>range.png</p> <pre> <code class="language-swift">let disposeBag = 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>repeatElement</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> <p>repeat.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.repeatElement(":red_circle:") .take(3) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">:red_circle: :red_circle: :red_circle:</code></pre> <h3>generate</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">let disposeBag = DisposeBag() Observable.generate( initialState: 0, condition: { $0 < 3 }, iterate: { $0 + 1 } ) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <h3>deferred</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>defered.png</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">let disposeBag = DisposeBag() var count = 1 let deferredSequence = Observable<String>.deferred { print("Creating \(count)") count += 1 return Observable.create { observer in print("Emitting...") observer.onNext(":dog:") observer.onNext(":cat:") observer.onNext(":monkey_face:") return Disposables.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... :dog: :cat: :monkey_face: Creating 2 Emitting... :dog: :cat: :monkey_face:</code></pre> <h3>error</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">let disposeBag = DisposeBag() Observable<Int>.error(TestError.test) .subscribe { print($0) } .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">error(test)</code></pre> <h3>doOn</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">let disposeBag = DisposeBag() Observable.of(":apple:", ":pear:", ":tangerine:", ":lemon:") .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: :apple: :apple: Intercepted: :pear: :pear: Intercepted: :tangerine: :tangerine: Intercepted: :lemon: :lemon: Completed 结束</code></pre> <h2>学会使用Subjects</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>PublishSubject</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> <p>publishsubject.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let subject = PublishSubject<String>() subject.addObserver("1").addDisposableTo(disposeBag) subject.onNext(":dog:") subject.onNext(":cat:") subject.addObserver("2").addDisposableTo(disposeBag) subject.onNext(":a:") subject.onNext(":b:")</code></pre> <pre> <code class="language-swift">Subscription: 1 Event: next(:dog:) Subscription: 1 Event: next(:cat:) Subscription: 1 Event: next(:a:) Subscription: 2 Event: next(:a:) Subscription: 1 Event: next(:b:) Subscription: 2 Event: next(:b:)</code></pre> <h3>ReplaySubject</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> <p>replaysubject.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let subject = ReplaySubject<String>.create(bufferSize: 1) subject.addObserver("1").addDisposableTo(disposeBag) subject.onNext(":dog:") subject.onNext(":cat:") subject.addObserver("2").addDisposableTo(disposeBag) subject.onNext(":a:") subject.onNext(":b:")</code></pre> <pre> <code class="language-swift">Subscription: 1 Event: next(:dog:) Subscription: 1 Event: next(:cat:) Subscription: 2 Event: next(:cat:) //订阅之后还可以接受一次前面发出的事件 Subscription: 1 Event: next(:a:) Subscription: 2 Event: next(:a:) Subscription: 1 Event: next(:b:) Subscription: 2 Event: next(:b:)</code></pre> <h3>BehaviorSubject</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> <p>behaviorsubject.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let subject = BehaviorSubject(value: ":red_circle:") subject.addObserver("1").addDisposableTo(disposeBag) subject.onNext(":dog:") subject.onNext(":cat:") subject.addObserver("2").addDisposableTo(disposeBag) subject.onNext(":a:") subject.onNext(":b:") subject.addObserver("3").addDisposableTo(disposeBag) subject.onNext(":pear:") subject.onNext(":tangerine:")</code></pre> <pre> <code class="language-swift">Subscription: 1 Event: next(:red_circle:) Subscription: 1 Event: next(:dog:) Subscription: 1 Event: next(:cat:) Subscription: 2 Event: next(:cat:) //订阅之前的最后一个事件 Subscription: 1 Event: next(:a:) Subscription: 2 Event: next(:a:) Subscription: 1 Event: next(:b:) Subscription: 2 Event: next(:b:) Subscription: 3 Event: next(:b:) //订阅之前的最后一个事件 Subscription: 1 Event: next(:pear:) Subscription: 3 Event: next(:pear:) Subscription: 2 Event: next(:pear:) Subscription: 1 Event: next(:tangerine:) Subscription: 3 Event: next(:tangerine:) Subscription: 2 Event: next(:tangerine:)</code></pre> <p>PublishSubject, ReplaySubject和BehaviorSubject是不会自动发出completed事件的。</p> <h3>Variable</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">let disposeBag = DisposeBag() let variable = Variable(":red_circle:") variable.asObservable().addObserver("1").addDisposableTo(disposeBag) variable.value = ":dog:" variable.value = ":cat:" variable.asObservable().addObserver("2").addDisposableTo(disposeBag) variable.value = ":a:" variable.value = ":b:"</code></pre> <pre> <code class="language-swift">Subscription: 1 Event: next(:red_circle:) Subscription: 1 Event: next(:dog:) Subscription: 1 Event: next(:cat:) Subscription: 2 Event: next(:cat:) Subscription: 1 Event: next(:a:) Subscription: 2 Event: next(:a:) Subscription: 1 Event: next(:b:) Subscription: 2 Event: next(:b:) Subscription: 1 Event: completed Subscription: 2 Event: completed</code></pre> <h2>联合操作</h2> <p>联合操作就是把多个Observable流合成单个Observable流</p> <h3>startWith</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> <p>startwith.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.of("2", "3") .startWith("1") .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <h3>merge</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> <p>merge.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let subject1 = PublishSubject<String>() let subject2 = PublishSubject<String>() Observable.of(subject1, subject2) .merge() .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) subject1.onNext(":a:") subject1.onNext(":b:") subject2.onNext("①") subject2.onNext("②") subject1.onNext(":ab:") subject2.onNext("③")</code></pre> <pre> <code class="language-swift">:a: :b: ① ② :ab: ③</code></pre> <h3>zip</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> <p>zip.png</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(":a:") stringSubject.onNext(":b:") intSubject.onNext(1) intSubject.onNext(2) stringSubject.onNext(":ab:") intSubject.onNext(3)</code></pre> <pre> <code class="language-swift">:a: 1 将stringSubject和intSubject压缩到一起共同处理 :b: 2 :ab: 3</code></pre> <h3>combineLatest</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> <p>combinlatest.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let stringSubject = PublishSubject<String>() let intSubject = PublishSubject<Int>() Observable.combineLatest(stringSubject, intSubject) { stringElement, intElement in "\(stringElement) \(intElement)" } .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) stringSubject.onNext(":a:") stringSubject.onNext(":b:") intSubject.onNext(1) intSubject.onNext(2) stringSubject.onNext(":ab:")</code></pre> <pre> <code class="language-swift">:b: 1 :b: 2 :ab: 2</code></pre> <h3>switchLatest</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> <p>switch.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() let subject1 = BehaviorSubject(value: ":soccer:️") let subject2 = BehaviorSubject(value: ":apple:") let variable = Variable(subject1) variable.asObservable() .switchLatest() .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag) subject1.onNext(":football:") subject1.onNext(":basketball:") variable.value = subject2 subject1.onNext(":baseball:") subject2.onNext(":pear:") variable.value = subject1 subject2.onNext("田腾飞") subject1.onNext("沸腾天")</code></pre> <pre> <code class="language-swift">:soccer:️ :football: :basketball: :apple: :pear: :baseball: 沸腾天</code></pre> <h2>变换操作</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> <p>transform.png</p> <pre> <code class="language-swift">let disposeBag = 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>flatMap</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> <p>flatmap.png</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() struct Player { var score: Variable<Int> //里面是一个Variable } let :boy|type_1_2: = Player(score: Variable(80)) let :girl|type_3: = Player(score: Variable(90)) let :joy: = Player(score: Variable(550)) let player = Variable(:boy|type_1_2:) //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) :boy|type_1_2:.score.value = 85 player.value = :girl|type_3: //更换了value，相当于又添加了一个sequence，两个sequence都可以接收 :boy|type_1_2:.score.value = 95 :boy|type_1_2:.score.value = 222 player.value = :joy: :girl|type_3:.score.value = 100</code></pre> <h3>flatMapLatest</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">let disposeBag = DisposeBag() Observable.of(10, 100, 1000) .scan(1) { aggregateValue, newValue in aggregateValue + newValue } .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <h2>过滤和约束</h2> <h3>filter</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">let disposeBag = DisposeBag() Observable.of( ":cat:", ":rabbit:", ":dog:", ":frog:", ":cat:", ":rabbit:", ":hamster:", ":frog:", ":cat:") .filter { $0 == ":cat:" } .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">:cat: :cat: :cat:</code></pre> <h3>distinctUntilChanged</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">let disposeBag = DisposeBag() Observable.of(":cat:", ":pig:", ":cat:", ":cat:", ":cat:", ":monkey_face:", ":cat:") .distinctUntilChanged() .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">:cat: :pig: :cat: :monkey_face: :cat:</code></pre> <h3>elementAt</h3> <p>只处理在指定位置的事件</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.of(":cat:", ":rabbit:", ":dog:", ":frog:", ":pig:", ":monkey_face:") .elementAt(3) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">:frog:</code></pre> <h3>single</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(":cat:", ":rabbit:", ":dog:", ":frog:", ":pig:", ":monkey_face:") .single() .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">:cat: //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(":cat:", ":rabbit:", ":dog:", ":frog:", ":pig:", ":monkey_face:") .single { $0 == ":frog:" } //青蛙只有一个，completed .subscribe { print($0) } .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">Observable.of(":cat:", ":rabbit:", ":dog:", ":cat:", ":rabbit:", ":dog:") .single { $0 == ":rabbit:" } //兔子有两个，会发出error .subscribe { print($0) } .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">Observable.of(":cat:", ":rabbit:", ":dog:", ":frog:", ":pig:", ":monkey_face:") .single { $0 == ":large_blue_circle:" } //没有蓝色球，会发出error .subscribe { print($0) } .addDisposableTo(disposeBag)</code></pre> <h3>take</h3> <p>只处理前几个事件信号,</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.of(":cat:", ":rabbit:", ":dog:", ":frog:", ":pig:", ":monkey_face:") .take(3) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">:cat: :rabbit: :dog:</code></pre> <h3>takeLast</h3> <p>只处理后几个事件信号</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.of(":cat:", ":rabbit:", ":dog:", ":frog:", ":pig:", ":monkey_face:") .takeLast(3) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">:frog: :pig: :monkey_face:</code></pre> <h3>takeWhile</h3> <p>当条件满足的时候进行处理</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.of(1, 2, 3, 4, 5, 6) .takeWhile { $0 < 4 } .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <h3>takeUntil</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(":cat:") sourceSequence.onNext(":rabbit:") sourceSequence.onNext(":dog:") referenceSequence.onNext(":red_circle:") //停止接收消息 sourceSequence.onNext(":frog:") sourceSequence.onNext(":pig:") sourceSequence.onNext(":monkey_face:")</code></pre> <pre> <code class="language-swift">next(:cat:) next(:rabbit:) next(:dog:) completed</code></pre> <h3>skip</h3> <p>取消前几个事件</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.of(":cat:", ":rabbit:", ":dog:", ":frog:", ":pig:", ":monkey_face:") .skip(2) .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <pre> <code class="language-swift">:dog: :frog: :pig: :monkey_face:</code></pre> <h3>skipWhile</h3> <p>满足条件的事件消息都取消</p> <pre> <code class="language-swift">let disposeBag = DisposeBag() Observable.of(1, 2, 3, 4, 5, 6) .skipWhile { $0 < 4 } .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <h3>skipWhileWithIndex</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(":cat:", ":rabbit:", ":dog:", ":frog:", ":pig:", ":monkey_face:") .skipWhileWithIndex { element, index in index < 3 } .subscribe(onNext: { print($0) }) .addDisposableTo(disposeBag)</code></pre> <h3>skipUntil</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(":cat:") sourceSequence.onNext(":rabbit:") sourceSequence.onNext(":dog:") referenceSequence.onNext(":red_circle:") sourceSequence.onNext(":frog:") sourceSequence.onNext(":pig:") sourceSequence.onNext(":monkey_face:") }</code></pre> <h2>数学操作</h2> <h3>toArray</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>reduce</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>concat</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: ":apple:") let subject2 = BehaviorSubject(value: ":dog:") let variable = Variable(subject1) variable.asObservable() .concat() .subscribe { print($0) } .addDisposableTo(disposeBag) subject1.onNext(":pear:") subject1.onNext(":tangerine:") variable.value = subject2 subject2.onNext(":cat:") //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(":mouse:")</code></pre> <pre> <code class="language-swift">next(:apple:) next(:pear:) next(:tangerine:) next(fei) next(:mouse:)</code></pre> <h2>连接性操作</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>publish</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>replay</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>multicast</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>错误处理</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">let disposeBag = DisposeBag() let sequenceThatFails = PublishSubject<String>() sequenceThatFails .catchErrorJustReturn(":blush:") .subscribe { print($0) } .addDisposableTo(disposeBag) sequenceThatFails.onNext(":grimacing:") sequenceThatFails.onNext(":fearful:") sequenceThatFails.onNext(":rage:") sequenceThatFails.onNext(":red_circle:") sequenceThatFails.onError(TestError.test)</code></pre> <pre> <code class="language-swift">next(:grimacing:) next(:fearful:) next(:rage:) next(:red_circle:) next(:blush:) completed</code></pre> <h3>catchError</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(":grimacing:") sequenceThatFails.onNext(":fearful:") sequenceThatFails.onNext(":rage:") sequenceThatFails.onNext(":red_circle:") sequenceThatFails.onError(TestError.test) recoverySequence.onNext(":blush:")</code></pre> <pre> <code class="language-swift">next(:grimacing:) next(:fearful:) next(:rage:) next(:red_circle:) Error: test next(:blush:)</code></pre> <h3>retry</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(":apple:") observer.onNext(":pear:") observer.onNext(":tangerine:") if count == 1 { observer.onError(TestError.test) print("Error encountered") count += 1 } observer.onNext(":dog:") observer.onNext(":cat:") observer.onNext(":mouse:") 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>debug</h2> <h3>debug</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>RxSwift.Resources.total</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> </p> <p>来自：http://www.jianshu.com/p/a1e2665f9a6c</p> <p> </p> 本文由用户 njhu5107 自行上传分享，仅供网友学习交流。所有权归原作者，若您的权利被侵害，请联系管理员。
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