ReactiveX 学习笔记（7）聚合操作符

Mathematical and Aggregate Operators

本文的主题为处理 Observable 的聚合操作符。

这里的 Observable 实质上是可观察的数据流。

RxJava操作符（八）Aggregate

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));
}

Average

ReactiveX - Average operator

Reactive Extensions再入門 その１６「最大、最少、平均を求めるメソッド」

Average 计算源数据流所有数据的平均值，然后发送这个平均值。

• RxNET

var s = new Subject<int>();
s.Average().Subscribe(avg =>
{
    Console.WriteLine("Average {0}", avg);
},
() => Console.WriteLine("Average Completed"));
Console.WriteLine("OnNext(1-3)");
s.OnNext(1);
s.OnNext(2);
s.OnNext(3);
Console.WriteLine("OnCompleted()");
s.OnCompleted();
/*
OnNext(1-3)
OnCompleted()
Average 2
Average Completed
*/

Concat

ReactiveX - Concat operator

Reactive Extensions再入門 その４１「どんどん合成するよ」

Concat 合并数据流，按照数据流的连接顺序依次发送各个数据流的数据。

给定两个数据流 A 和 B，Concat(A, B) 会先发送 A 中的数据，等到 A 中的数据全部发送完毕后再发送 B 中的数据。多个数据流也以此类推。

• RxNET

var s1 = Observable.Range(0, 3);
var s2 = Observable.Range(5, 5);
s1.Concat(s2)
.Subscribe(Console.WriteLine);
/*
0
1
2
5
6
7
8
9
*/

private static IEnumerable<IObservable<long>> GetSequences()
{
    Console.WriteLine("GetSequences() called");
    Console.WriteLine("Yield 1st sequence");
    yield return Observable.Create<long>(o =>
    {
        Console.WriteLine("1st subscribed to");
        return Observable.Timer(TimeSpan.FromMilliseconds(500))
        .Select(i => 1L)
        .Subscribe(o);
    });
    Console.WriteLine("Yield 2nd sequence");
    yield return Observable.Create<long>(o =>
    {
        Console.WriteLine("2nd subscribed to");
        return Observable.Timer(TimeSpan.FromMilliseconds(300))
        .Select(i => 2L)
        .Subscribe(o);
    });
    Thread.Sleep(1000);     //Force a delay
    Console.WriteLine("Yield 3rd sequence");
    yield return Observable.Create<long>(o =>
    {
        Console.WriteLine("3rd subscribed to");
        return Observable.Timer(TimeSpan.FromMilliseconds(100))
        .Select(i => 3L)
        .Subscribe(o);
    });
    Console.WriteLine("GetSequences() complete");
}
GetSequences().Concat().Dump("Concat");
/*
GetSequences() called
Yield 1st sequence
1st subscribed to
Concat-->1
Yield 2nd sequence
2nd subscribed to
Concat-->2
Yield 3rd sequence
3rd subscribed to
Concat-->3
GetSequences() complete
Concat completed
*/

• RxJava

val seq1 = Observable.range(0, 3)
val seq2 = Observable.range(10, 3)
Observable.concat(seq1, seq2)
    .dump()
/*
onNext: 0
onNext: 1
onNext: 2
onNext: 10
onNext: 11
onNext: 12
onComplete
*/

val words = Observable.just(
    "First",
    "Second",
    "Third",
    "Fourth",
    "Fifth",
    "Sixth"
)
Observable.concat(words.groupBy { v -> v[0] })
    .dump()
/*
onNext: First
onNext: Fourth
onNext: Fifth
onNext: Second
onNext: Sixth
onNext: Third
onComplete
*/

val seq1 = Observable.range(0, 3)
val seq2 = Observable.range(10, 3)
val seq3 = Observable.just(20)
seq1.concatWith(seq2)
    .concatWith(seq3)
    .dump()
/*
onNext: 0
onNext: 1
onNext: 2
onNext: 10
onNext: 11
onNext: 12
onNext: 20
onComplete
*/

• RxSwift

let disposeBag = DisposeBag()
let subject1 = BehaviorSubject(value: "