ReactiveX 学习笔记（3）转换数据流

Transforming Observables

本文的主题为转换 Observable 的操作符。

这里的 Observable 实质上是可观察的数据流。

RxJava操作符（二）Transforming Observables

公共代码

• RxNET

public static void Dump<T>(this IObservable<T> source, string name)
{
    source.Subscribe(
    i => Console.WriteLine("{0}-->{1}", name, i),
    ex => Console.WriteLine("{0} failed-->{1}", name, ex.Message),
    () => Console.WriteLine("{0} completed", name));
}

• RxJava

fun <T> Observable<T>.dump() =
    this.subscribe({ println("onNext: $it") },
        { println("onError: $it: ${it.message}") },
        { println("onComplete") })
fun <T> Observable<T>.dump(name: String) =
    this.subscribe({ println("$name: onNext: $it") },
        { println("$name: onError: $it: ${it.message}") },
        { println("$name: onComplete") })

Buffer

ReactiveX - Buffer operator

Reactive Extensions再入門 その２５「値をまとめるBufferメソッド」

Buffer 转换数据流：间隔性地将数据流中邻近的数据打包，形成数据包的数据流。

这里的数据包即静态的数组。

• RxNET

var source = Observable.Interval(TimeSpan.FromSeconds(1)).Take(10);
source.Buffer(3, 1)
.Subscribe(
buffer =>
{
    Console.WriteLine("--Buffered values");
    foreach (var value in buffer)
        Console.WriteLine(value);
}, () => Console.WriteLine("Completed"));
/*
--Buffered values
0
1
2
--Buffered values
1
2
3
..
--Buffered values
7
8
9
--Buffered values
8
9
--Buffered values
9
Completed
*/

• RxJava

Observable.range(0, 10)
    .buffer(4)
    .dump()
/*
onNext: [0, 1, 2, 3]
onNext: [4, 5, 6, 7]
onNext: [8, 9]
onComplete
*/

Observable.interval(100, TimeUnit.MILLISECONDS).take(10)
    .buffer(250, TimeUnit.MILLISECONDS)
    .dump()
/*
onNext: [0, 1]
onNext: [2, 3, 4]
onNext: [5, 6]
onNext: [7, 8, 9]
onNext: []
onComplete
*/

Observable.interval(100, TimeUnit.MILLISECONDS)
    .take(10)
    .buffer(250, TimeUnit.MILLISECONDS, 2)
    .dump()
/*
onNext: [0, 1]
onNext: []
onNext: [2, 3]
onNext: []
onNext: [4, 5]
onNext: [6]
onNext: [7, 8]
onNext: [9]
onNext: []
onComplete
*/

Observable.interval(100, TimeUnit.MILLISECONDS).take(10)
    .buffer(Observable.interval(250, TimeUnit.MILLISECONDS))
    .dump()
/*
onNext: [0, 1]
onNext: [2, 3]
onNext: [4, 5, 6]
onNext: [7, 8, 9]
onNext: []
onComplete
*/

Observable.range(0, 10)
    .buffer(4, 3)
    .dump()
/*
onNext: [0, 1, 2, 3]
onNext: [3, 4, 5, 6]
onNext: [6, 7, 8, 9]
onNext: [9]
onComplete
*/

Observable.interval(100, TimeUnit.MILLISECONDS).take(10)
    .buffer(350, 200, TimeUnit.MILLISECONDS)
    .dump()
/*
onNext: [0, 1, 2]
onNext: [2, 3, 4]
onNext: [3, 4, 5, 6]
onNext: [6, 7, 8]
onNext: [7, 8, 9]
onNext: []
onComplete
*/

Observable.interval(100, TimeUnit.MILLISECONDS).take(10)
    .buffer<Long, Long>(
        Observable.interval(250, TimeUnit.MILLISECONDS),
        Function { i -> Observable.timer(200, TimeUnit.MILLISECONDS) } )
    .dump()
/*
onNext: [2, 3]
onNext: [5, 6]
onNext: [7, 8]
onNext: []
onComplete
*/

FlatMap / SelectMany

ReactiveX - FlatMap operator

Reactive Extensions再入門 その４０「IObservableの合成はじめました」

FlatMap / SelectMany 转换数据流：将源数据流的每一项都转换成数据流，从而形成数据流的数据流，最后再平坦化将两维数据流合并成一个数据流。

• RxNET

Observable.Range(1, 3)
.SelectMany(i => Observable.Range(1, i))
.Dump("SelectMany");
/*
SelectMany-->1
SelectMany-->1
SelectMany-->2
SelectMany-->1
SelectMany-->2
SelectMany-->3
SelectMany completed
*/

• RxJava

val values = Observable.just(2)
values
    .flatMap { i -> Observable.range(0, i) }
    .dump()
/*
onNext: 0
onNext: 1
onComplete
*/

val values = Observable.range(1, 3)
values
    .flatMap { i -> Observable.range(0, i) }
    .dump()
/*
onNext: 0
onNext: 0
onNext: 1
onNext: 0
onNext: 1
onNext: 2
onComplete
*/

val values = Observable.just(1)
values
    .flatMap { i ->
        Observable.just(
            Character.valueOf((i + 64).toChar())
        )
    }
    .dump()
/*
onNext: A
onComplete
*/

val values = Observable.range(0, 30)
values
    .flatMap<Char> { i ->
        if (i in 1..26)
            Observable.just(Character.valueOf((i + 64).toChar()))
        else
            Observable.empty()
    }
    .dump()
/*
onNext: A
onNext: B
...
onNext: Y
onNext: Z
onComplete
*/

Observable.just(100, 150)
    .flatMap { i ->
        Observable.interval(i.toLong(), TimeUnit.MILLISECONDS)
            .map { v -> i }
    }
    .take(10)
    .dump()
/*
onNext: 100
onNext: 150
onNext: 100
onNext: 150
onNext: 100
onNext: 100
onNext: 150
onNext: 100
onNext: 100
onNext: 150
onComplete
*/

Observable.just(100, 150)
    .concatMap { i ->
        Observable.interval(i.toLong(), TimeUnit.MILLISECONDS)
            .map { v -> i }
            .take(3)
    }
    .dump()
/*
onNext: 100
onNext: 100
onNext: 100
onNext: 150
onNext: 150
onNext: 150
onComplete
*/

Observable.interval(100, TimeUnit.MILLISECONDS)
    .switchMap { i ->
        Observable.interval(30, TimeUnit.MILLISECONDS)
            .map { l -> i }
    }
    .take(9)
    .dump()
/*
onNext: 0
onNext: 0
onNext: 0
onNext: 1
onNext: 1
onNext: 1
onNext: 2
onNext: 2
onNext: 2
onComplete
*/

• concatMap / flatMap / switchMap

• flatMapIterable

Observable.range(1, 3)
    .flatMapIterable { i -> 1..i }
    .dump()
/*
onNext: 1
onNext: 1
onNext: 2
onNext: 1
onNext: 2
onNext: 3
onComplete
*/

Observable.range(1, 3)
    .flatMapIterable<Int, Int>(
        { i -> 1..i },
        { ori, rv -> ori * rv })
    .dump()
/*
onNext: 1
onNext: 2
onNext: 4
onNext: 3
onNext: 6
onNext: 9
onComplete
*/

Observable.range(1, 3)
    .flatMapIterable<Int, Int>(
        { i -> generateSequence(1) { (it + 1).takeIf { it <= i } }.asIterable() },
        { ori, rv -> ori * rv })
    .dump()
/*
onNext: 1
onNext: 2
onNext: 4
onNext: 3
onNext: 6
onNext: 9
onComplete
*/

• RxSwift

let disposeBag = DisposeBag()
struct Player {
    var score: Variable<Int>
}
let