本文是示例主要来自于官方的实例代码，可从这里下载，实例代码稍有改动。其中的图片来自于reactivex.io/

本文主要的作用是查看实例代码并查看对应实例代码的效果，不需要运行项目

操作符目录

RxSwift官方使用示例之<创建和订阅Observables>
- never、empty、just、of、from、create、range、repeatElement、generate、deferred、error、doOn
RxSwift官方使用示例之<使用Subjects>
- PublishSubject、ReplaySubject、BehaviorSubject
RxSwift官方使用示例之<组合操作符>
- startWith、merge、zip、combineLatest、Array.combineLatest、switchLatest、withLatestFrom
RxSwift官方使用示例之<转换操作符>
- map、flatMap 和 flatMapLatest、scan
RxSwift官方使用示例之<过滤及条件操作符>
- filter、distinctUntilChanged、elementAt、single、take、takeLast、takeWhile、takeUntil、skip、skipWhile、skipWhileWithIndex、skipUntil
RxSwift官方使用示例之<数学和聚合操作符>
- toArray、reduce、concat
RxSwift官方使用示例之<可连接操作符>
- interval、publish、replay、multicast
RxSwift官方使用示例之<错误处理操作符>
- catchAndReturn、catchError、retry、retry(_:)

debug 操作符会打印所有的 subscriptions, events, disposals

filter

只发出 Observable 序列中满足指定条件的元素

let disposeBag = DisposeBag()
        
Observable.of(2, 30, 22, 5, 60, 1)
    .filter {
        $0 > 10
    }
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)

打印

30
22
60

distinctUntilChanged

抑制由 Observable 序列发出的连续重复元素

let disposeBag = DisposeBag()
    
Observable.of(1, 2, 2, 1, 3)
    .distinctUntilChanged()
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)

打印

elementAt

只发射 Observable 序列指定索引处的元素

let disposeBag = DisposeBag()
        
Observable.of(1, 2, 3, 4)
    .element(at: 2)
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)

打印

single

仅发射 Observable 序列发射的第一个元素（或第一个满足条件的元素）。如果 Observable 序列没有发出恰好一个元素，则会抛出错误

let disposeBag = DisposeBag()
        
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
    .single()
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)

打印

🐱
Unhandled error happened: Sequence contains more than one element.

此时会有错误信息打印，如果想处理该错误信息，可以加上 onError:，如下

let disposeBag = DisposeBag()
                
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
    .single()
    .subscribe(onNext: { print($0) }, onError: { print("出错啦：", $0) } )
    .disposed(by: disposeBag)

打印

🐱
出错啦： Sequence contains more than one element.

此外，single 还可以加上条件判断

let disposeBag = DisposeBag()
        
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
    .single { $0 == "🐸" }
    .subscribe { print($0) }
    .disposed(by: disposeBag)

Observable.of("🐱", "🐰", "🐶", "🐱", "🐰", "🐶")
    .single { $0 == "🐰" }
    .subscribe { print($0) }
    .disposed(by: disposeBag)

Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
    .single { $0 == "🔵" }
    .subscribe { print($0) }
    .disposed(by: disposeBag)

打印

next(🐸)
completed
next(🐰)
error(Sequence contains more than one element.)
error(Sequence doesn't contain any elements.)

从打印可以看出，第一个打印正常，输出一个结果之后立即completed；第二个打印异常，因为有2个🐰，所以抛出异常 error(Sequence contains more than one element.)；第三个也异常，因为序列中没有🔵，抛出异常error(Sequence doesn't contain any elements.)

take

仅从 Observable 序列的开头发出指定数量的元素

let disposeBag = DisposeBag()
    
Observable.of(1, 2, 3, 4)
    .take(2)
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)

打印

1
2

takeLast

仅从 Observable 序列的末尾发出指定数量的元素

let disposeBag = DisposeBag()
    
Observable.of(1, 2, 3, 4)
    .take(1)
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)

打印

takeWhile

从 Observable 序列的开头发出满足条件的元素

let disposeBag = DisposeBag()
            
Observable.of(1, 2, 3, 4, 5, 6)
    .take(while: { $0 < 4 } )
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)

打印

1
2
3

takeUntil

从源 Observable 序列中发出元素，直到引用 Observable 序列发出元素

let disposeBag = DisposeBag()
        
let sourceSequence = PublishSubject<String>()
let referenceSequence = PublishSubject<String>()

sourceSequence
    .take(until: referenceSequence)
    .subscribe { print($0) }
    .disposed(by: disposeBag)

sourceSequence.onNext("1")
sourceSequence.onNext("2")
sourceSequence.onNext("3")
sourceSequence.onNext("3")
sourceSequence.onNext("4")
sourceSequence.onNext("5")

referenceSequence.onNext("0")

sourceSequence.onNext("6")
sourceSequence.onNext("7")
sourceSequence.onNext("8")

referenceSequence.onNext("0")

sourceSequence.onNext("9")

打印

next(1)
next(2)
next(3)
next(3)
next(4)
next(5)
completed

skip

从 Observable 序列的开头跳过发射指定数量的元素

let disposeBag = DisposeBag()
        
Observable.of(1, 2, 3, 4)
    .skip(2)
    .subscribe { print($0) }
    .disposed(by: disposeBag)

打印

next(3)
next(4)
completed

skipWhile

从 Observable 序列的开头跳过发射满足条件的元素

let disposeBag = DisposeBag()

Observable.of(1, 2, 3, 4, 5, 6)
    .skip(while: { $0 < 4 } )
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)

打印

4
5
6

skipWhileWithIndex