RxSwift基本使用（一）

本文主要是介绍RxSwift基本使用（一），希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

RxSwift基本使用（一）

备注：本文参考自田腾飞博文 [RxSwift入坑解读-你所需要知道的各种概念] (http://www.codertian.com/2016/11/27/RxSwift-ru-keng-ji-read-document/)，出于个人学习以及笔记需要特记录下RxSwift基本使用

概念

Observable : 可被观察的，事件源

Observer : 观察者，观察者需要订阅Observable，才能受到其发出的事件

DisposeBag : 相当于iOS中的ARC，会在适当的时候销毁观察者，自动去释放资源

如果需要手动销毁观察者直接调用dispose()方法,例：
Observable.empty().subscribe { (str:Event) in
print(“empty:”,str)
}.dispose()

subscribe : 订阅者，用于订阅sequence发出的事件

基本使用

never

never就是创建一个sequence,但不发出任何事件信号

let bag = DisposeBag()
Observable.never().subscribe { (str :Event<String>) inprint("never:",str) //无
}.addDisposableTo(bag)

备注：为了方便简洁，后续例子中创建bag变量的代码将省略

empty

empty创建一个空的sequence,但只能发出一个completed事件

Observable.empty().subscribe { (str :Event<String>) inprint("empty:",str)
}.addDisposableTo(bag)//empty: completed

just

just创建一个sequence,但只能发出一种特定的事件，能正常结束

Observable.just("just").subscribe { (str :Event<String>) inprint("just:",str)
}.addDisposableTo(bag)//just:next(just) 
//just:completed

of

创建一个sequence能发出很多种事件信号

Observable.of("1","2","3").subscribe { (str) inprint("of:",str)
}.addDisposableTo(bag)/**of: next(1)of: next(2)of: next(3)of: completed*///subscribe onNext 直接取值Observable.of("1","2","3").subscribe(onNext: { (str) inprint("of2:",str)}).addDisposableTo(bag)/**of2: 1of2: 2of2: 3*/

from

from从集合中创建sequence，例如数组，字典或者Set

    Observable.from([10,100,1000]).subscribe(onNext: { (num) inprint("from:",num)}).addDisposableTo(bag)/**from: 10from: 100from: 1000**/

create

create 自定义可观察的sequence

    //create 自定义可观察的sequencelet myObservable = Observable.create { (observer:AnyObserver<Any>) -> Disposable inobserver.onNext("12")observer.onNext("21")observer.onNext("123")observer.onCompleted()return Disposables.create()}myObservable.subscribe { (e:Event<Any>) inprint("myObservable:",e)}.addDisposableTo(bag)/**myObservable: next(12)myObservable: next(21)myObservable: next(123)myObservable: completed**/

range

range 创建一个sequence，会发出这个范围中所有事件

    Observable.range(start: 1, count: 5).subscribe(onNext: { (num) inprint("range:",num)}).addDisposableTo(bag)/**range: 1range: 2range: 3range: 4range: 5**/

repeatElement

创建一个sequence，发出特定的事件n次

Observable.repeatElement("LouKit").take(3).subscribe { print($0)}.addDisposableTo(bag)//重复发出3次，如果没有take 就无限次/**next(LouKit)next(LouKit)next(LouKit)completed**/

generate

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

    Observable.generate(initialState: 10, condition: {$0 < 15}, iterate: {$0 + 1}).subscribe(onNext: {print("generate",$0)}).addDisposableTo(bag)/**generate 10generate 11generate 12generate 13generate 14**/

deferred

deferred会为每一为订阅者observer创建一个新的可观察序列

    var index = 1let deferred = Observable<String>.deferred{print("index:",index)index += 1return Observable.create{ observer inobserver.onNext("1")observer.onNext("2")observer.onCompleted()return Disposables.create()}}deferred.subscribe { print("调用1:",$0)}.addDisposableTo(bag)deferred.subscribe { print("调用2:",$0)}.addDisposableTo(bag)/**index: 1调用1: next(1)调用1: next(2)调用1: completedindex: 2调用2: next(1)调用2: next(2)调用2: completed**/

do

主要用于在subscribe中onNext，onError，onCompleted前调用

    Observable.just("00").do(onNext: {print("doOnNext:",$0)},onError: {print("doOnError:",$0)},onCompleted: {print("doOnCompleted:")}).subscribe(onNext: { (str) inprint("onNext:",str)}, onError: { (error) inprint("onError")}, onCompleted: {print("onCompleted")}).addDisposableTo(bag)/**doOnNext: 00onNext: 00doOnCompleted:onCompleted**/

Subjects

Subjet是observable和Observer之间的桥梁，一个Subject既可以充当Obserable也可以充当Observer，即它可以发出事件，也可以监听事件

PublishSubject

采用PublishSubject订阅事件的时候，只能接收到订阅他之后发生的事件

    let publicSubject = PublishSubject<String>()publicSubject.onNext("A")publicSubject.onNext("B")publicSubject.subscribe(onNext: {print("publicSubject:",$0)}) .addDisposableTo(bag)publicSubject.onNext("C")publicSubject.onNext("D")/**publicSubject: CpublicSubject: D**/

ReplaySubject

可以接收到订阅他之后以及之前发生的事件,对于要接受几个以前的事件取决于bufferSize设置的大小

    let replaySubject = ReplaySubject<String>.create(bufferSize: 2)replaySubject.onNext("A")replaySubject.onNext("B")replaySubject.onNext("C")replaySubject.onNext("D")replaySubject.subscribe(onNext: {print("replaySubject:",$0)}) .addDisposableTo(bag)replaySubject.onNext("E")replaySubject.onNext("F")replaySubject.onNext("G")/**replaySubject: CreplaySubject: DreplaySubject: EreplaySubject: FreplaySubject: G**///接受全部的事件let replaySubject2 = ReplaySubject<String>.createUnbounded()replaySubject2.onNext("A")replaySubject2.onNext("B")replaySubject2.subscribe(onNext: {print("replaySubject2:",$0)}) .addDisposableTo(bag)replaySubject2.onNext("E")replaySubject2.onNext("F")/**replaySubject2: AreplaySubject2: BreplaySubject2: EreplaySubject2: F**/

BehaviorSubject

采用BehaviorSubject订阅事件，会接收到订阅之前的最后一个事件以及订阅之后所有事件。

    let behavior = BehaviorSubject(value: "behavior")behavior.onNext("A")behavior.onNext("B")behavior.subscribe(onNext: {print("behavior:",$0)}).addDisposableTo(bag)behavior.onNext("C")behavior.onNext("D")/**behavior: Bbehavior: Cbehavior: D**/

Variable

Variable是对BehaviorSubject一个包装；

Variable当成Obserable, 让订阅者进行订阅时, 需要asObserable转成Obserable；

Variable发出事件, 直接修改对象的value即可;

当事件结束时,Variable会自动发出completed事件

    let variable = Variable("variable")variable.value = "A"variable.value = "B"variable.asObservable().subscribe { (event:Event<String>) inprint("variable:",event)}.addDisposableTo(bag)variable.value = "C"variable.value = "D"/**variable: next(B)variable: next(C)variable: next(D)variable: completed**/

联合操作

联合操作就是把多个Observable流合成单个Observable流

startWith

在发出事件消息之前，先发出某个特定的事件消息。

    Observable.of(1,2).startWith(3).subscribe(onNext: {print($0)}).addDisposableTo(bag)    /**312**/

merge

将多个Observable流合成单个Observable流，然后任何一个Observable发出事件都能被接收到

    let sub1 = PublishSubject<String>()let sub2 = PublishSubject<String>()Observable.of(sub1,sub2).merge().subscribe(onNext: { print($0) }).addDisposableTo(bag)sub1.onNext("sub1-1")sub1.onNext("sub1-2")sub2.onNext("sub2-1")sub1.onNext("sub1-2")sub2.onNext("sub2-2")/**sub1-1sub1-2sub2-1sub1-2sub2-2**/

zip

将多个Observable流合成单个Observable流，只有当多个Observable流同时发出事件时，并且把多个Observable流的内容合并成一个元组，才会触发压缩流的事件。

    let zip1 = PublishSubject<String>()let zip2 = PublishSubject<String>()Observable.zip(zip1,zip2){ zip1,zip2 in"\(zip1) \(zip2)"}.subscribe(onNext: { print($0) }).addDisposableTo(bag)zip1.onNext("zip1-1")zip1.onNext("zip1-2")zip2.onNext("zip2-1")zip2.onNext("zip2-2")/**zip1-1 zip2-1zip1-2 zip2-2**/

注意：merge、zip都能将多个Observable流合成单个Observable流，但合并后前者任何一个Observable发出事件都能被接收到，后者必须是多个流同时发出事件时才被接收到

combineLatest

将多个Observable流合并起来 并拿到其各个流的最新值,即每个合并的signal至少都有过一次onNext，才会触发合并的流

    let ps1 = PublishSubject<String>()let ps2 = PublishSubject<String>()Observable.combineLatest(ps1, ps2) { element1, element2 in"\(element1) \(element2)"}.subscribe(onNext: { print($0) }).addDisposableTo(bag)ps1.onNext("ps1-01")ps1.onNext("ps1-02")ps2.onNext("ps2-01")/**ps1-02 ps2-01**/

switchLatest

用于对事件流进行转换，即一个Observable中的内容还是Observable。(个人理解)

    let bs1 = BehaviorSubject(value: "1")let bs2 = BehaviorSubject(value: "A")let variable = Variable(bs1)variable.asObservable().switchLatest().subscribe(onNext: {print($0)}).addDisposableTo(bag)bs1.onNext("2")variable.value = bs2bs1.onNext("3")bs2.onNext("B")/**12AB**/

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