ReactiveX 学习笔记（10）可链接的数据流

时间  2020-05-10
标签 reactivex 学习 笔记 链接 数据流 繁體版
原文   原文链接

Connectable Observable Operators

本文的主题为处理 Connectable Observable 的操做符。 这里的 Observable 实质上是可观察的数据流。html

RxJava操做符（九）Connectable Observable Operatorsjava

冷数据流 / 热数据流 / 可链接的数据流

  • 冷数据流只有在订阅后才开始发送数据。 订阅者能够保证观察到冷数据流最初所发送的数据。可是不一样的订阅者所观察到的不是同一份数据，是冷数据流专为本身发送的数据。冷数据流不能共享数据。
  • 热数据流从建立之初就开始发送数据，不管有没有订阅者都一直在发送数据。 订阅者只能观察到订阅以后热数据流所发送的数据。可是全部的订阅者所观察到的都是同一份数据。热数据流可以共享数据。
  • 可链接的数据流在链接以后将转变为热数据流，不管有没有订阅者都开始发送数据。
  • Interval 所建立的数据流是冷数据流

<!-- -->react

  • RxNET
Console.WriteLine(MethodBase.GetCurrentMethod().Name);
var observable = Observable.Interval(TimeSpan.FromSeconds(1));
using (observable.Subscribe(i => Console.WriteLine("first subscription : {0}", i)))
{
    Thread.Sleep(TimeSpan.FromSeconds(1.5));
    using (observable.Subscribe(i => Console.WriteLine("second subscription : {0}", i)))
        Console.ReadKey();
}
/*
first subscription : 0
first subscription : 1
second subscription : 0
first subscription : 2
second subscription : 1
first subscription : 3
...
*/
  • RxJava
val cold = Observable
    .interval(200, TimeUnit.MILLISECONDS)
    .take(5)
cold.dump("First")
Thread.sleep(500)
cold.dump("Second")
/*
First: onNext: 0
First: onNext: 1
First: onNext: 2
Second: onNext: 0
First: onNext: 3
Second: onNext: 1
First: onNext: 4
First: onComplete
Second: onNext: 2
Second: onNext: 3
Second: onNext: 4
Second: onComplete
*/
  • RxSwift
let interval = Observable<Int>.interval(1, scheduler: MainScheduler.instance)
_ = interval
    .subscribe(onNext: { print("Subscription: 1, Event: \($0)") })
delay(5) {
    _ = interval
        .subscribe(onNext: { print("Subscription: 2, Event: \($0)") })
}
/*
Subscription: 1, Event: 0
Subscription: 1, Event: 1
Subscription: 1, Event: 2
Subscription: 1, Event: 3
Subscription: 1, Event: 4
Subscription: 1, Event: 5
Subscription: 2, Event: 0
Subscription: 1, Event: 6
Subscription: 2, Event: 1
Subscription: 1, Event: 7
Subscription: 2, Event: 2
Subscription: 1, Event: 8
...
*/

Connect / Publish / PublishLast / MultiCast

ReactiveX - Connect operator ReactiveX - Publish operator Reactive Extensions再入門 その３６「ColdからHotへ！Publishメソッドと参照カウンタ？RefCountメソッド」 Reactive Extensions再入門 その３７「ColdからHotへ！その他のPublish系メソッド」swift

Publish / PublishLast 将普通数据流发布（转变）为可链接的数据流。 可链接的数据流必须经 Connect 链接后才开始发送数据。 Connect 链接可链接的数据流，将可链接的数据流变为热数据流并开始发送数据。 通过 Publish 发布，Connect 链接后的热数据流在订阅以后能够观察到订阅以后热数据流发送的数据。 通过 PublishLast 发布，Connect 链接后的热数据流在订阅以后只能观察到订阅以后热数据流最后发送的数据。 Publish / PublishLast 的返回值表明数据流对象，销毁该对象将销毁源数据流。 Connect 的返回值表明链接对象，销毁该对象将断开链接，被断开链接的热数据流将变回可链接的数据流。缓存

Multicast 的语义以下ide

  • .Publish() = .Multicast(new Subject<T>)
  • .PublishLast() = .Multicast(new AsyncSubject<T>)
  • .Replay() = .Multicast(new ReplaySubject<T>)

Publish PublishLast

  • RxNET
var observable = Observable.Interval(TimeSpan.FromSeconds(1)).Publish();
observable.Connect();
using (observable.Subscribe(i => Console.WriteLine("first subscription : {0}", i)))
{
    Thread.Sleep(TimeSpan.FromSeconds(2));
    using (observable.Subscribe(i => Console.WriteLine("second subscription : {0}", i)))
        Console.ReadKey();
}
/*
first subscription : 0
first subscription : 1
second subscription : 1
first subscription : 2
second subscription : 2
...
*/
var period = TimeSpan.FromSeconds(1);
var observable = Observable.Interval(TimeSpan.FromSeconds(1)).Publish();
using (observable.Subscribe(i => Console.WriteLine("first subscription : {0}", i)))
{
    Thread.Sleep(TimeSpan.FromSeconds(2));
    using (observable.Subscribe(i => Console.WriteLine("second subscription : {0}", i)))
    {
        observable.Connect();
        Console.ReadKey();
    }
}
/*
first subscription : 0
second subscription : 0
first subscription : 1
second subscription : 1
first subscription : 2
second subscription : 2
...
*/
var period = TimeSpan.FromSeconds(1);
var observable = Observable.Interval(period).Publish();
observable.Subscribe(i => Console.WriteLine("subscription : {0}", i));
var exit = false;
while (!exit)
{
    Console.WriteLine("Press enter to connect, esc to exit.");
    var key = Console.ReadKey(true);
    if (key.Key == ConsoleKey.Enter)
    {
        var connection = observable.Connect(); //--Connects here--
        Console.WriteLine("Press any key to dispose of connection.");
        Console.ReadKey();
        connection.Dispose(); //--Disconnects here--
    }
    if (key.Key == ConsoleKey.Escape)
    {
        exit = true;
    }
}
/*
Press enter to connect, esc to exit.
Press any key to dispose of connection.
subscription : 0
subscription : 1
subscription : 2
subscription : 3
Press enter to connect, esc to exit.
Press any key to dispose of connection.
subscription : 0
subscription : 1
subscription : 2
Press enter to connect, esc to exit.
...
*/
var period = TimeSpan.FromSeconds(1);
var observable = Observable.Interval(period)
.Do(l => Console.WriteLine("Publishing {0}", l)) //Side effect to show it is running
.Publish();
var subscription2 = observable.Connect();
Console.WriteLine("Press any key to subscribe");
Console.ReadKey();
var subscription = observable.Subscribe(i => Console.WriteLine("subscription : {0}", i));
Console.WriteLine("Press any key to unsubscribe.");
Console.ReadKey();
subscription.Dispose();
Console.WriteLine("Press any key to exit.");
Console.ReadKey();
subscription2.Dispose();
/*
Press any key to subscribe
Publishing 0
Publishing 1
Publishing 2
Press any key to unsubscribe.
Publishing 3
subscription : 3
Publishing 4
subscription : 4
Publishing 5
subscription : 5
Press any key to exit.
Publishing 6
Publishing 7
...
*/
  • PublishLast
var period = TimeSpan.FromSeconds(1);
var observable = Observable.Interval(period)
.Take(5)
.Do(l => Console.WriteLine("Publishing {0}", l)) //side effect to show it is running
.PublishLast();
observable.Connect();
Console.WriteLine("Press any key to subscribe");
Console.ReadKey();
var subscription = observable.Subscribe(i => Console.WriteLine("subscription : {0}", i));
Console.WriteLine("Press any key to unsubscribe.");
Console.ReadKey();
subscription.Dispose();
Console.WriteLine("Press any key to exit.");
Console.ReadKey();
/*
Press any key to subscribe
Publishing 0
Publishing 1
Publishing 2
Press any key to unsubscribe.
Publishing 3
Publishing 4
subscription : 4
Press any key to exit.
*/
  • RxJava
val cold = Observable.interval(200, TimeUnit.MILLISECONDS).publish()
cold.connect()
val s1 = cold.dump("First")
Thread.sleep(500)
val s2 = cold.dump("Second")
readLine()
s1.dispose()
s2.dispose()
/*
First: onNext: 0
First: onNext: 1
First: onNext: 2
Second: onNext: 2
First: onNext: 3
Second: onNext: 3
...
*/
val connectable = Observable.interval(200, TimeUnit.MILLISECONDS).publish()
var s = connectable.connect()
connectable.dump()
Thread.sleep(1000)
println("Closing connection")
s.dispose()
Thread.sleep(1000)
println("Reconnecting")
s = connectable.connect()
connectable.dump()
readLine()
s.dispose()
/*
onNext: 0
onNext: 1
onNext: 2
onNext: 3
Closing connection
onNext: 4
Reconnecting
onNext: 0
onNext: 1
onNext: 2
...
*/
val connectable = Observable.interval(200, TimeUnit.MILLISECONDS).publish()
connectable.connect()
val s1 = connectable.dump("First")
Thread.sleep(500)
val s2 = connectable.dump("Second")
Thread.sleep(500)
println("Disposing second")
s2.dispose()
readLine()
s1.dispose()
/*
First: onNext: 0
First: onNext: 1
First: onNext: 2
Second: onNext: 2
First: onNext: 3
Second: onNext: 3
Disposing second
First: onNext: 4
First: onNext: 5
First: onNext: 6
...
*/
  • RxSwift
let intSequence = Observable<Int>.interval(1, scheduler: MainScheduler.instance)
    .publish()
_ = intSequence
    .subscribe(onNext: { print("Subscription 1:, Event: \($0)") })
delay(2) { _ = intSequence.connect() }
delay(4) {
    _ = intSequence
        .subscribe(onNext: { print("Subscription 2:, Event: \($0)") })
}
delay(6) {
    _ = intSequence
        .subscribe(onNext: { print("Subscription 3:, Event: \($0)") })
}
/*
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 2:, Event: 3
Subscription 3:, Event: 3
Subscription 1:, Event: 4
Subscription 2:, Event: 4
Subscription 3:, Event: 4
...
*/
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)") })
}
delay(6) {
    _ = intSequence
        .subscribe(onNext: { print("\tSubscription 3:, Event: \($0)") })
}
/*
Subject: 0
	Subscription 1:, Event: 0
Subject: 1
	Subscription 1:, Event: 1
	Subscription 2:, Event: 1
Subject: 2
	Subscription 1:, Event: 2
	Subscription 2:, Event: 2
Subject: 3
	Subscription 1:, Event: 3
	Subscription 2:, Event: 3
	Subscription 3:, Event: 3
...
*/

RefCount

ReactiveX - RefCount operator Reactive Extensions再入門 その３６「ColdからHotへ！Publishメソッドと参照カウンタ？RefCountメソッド」ui

RefCount 将可链接的数据流从新变回普通数据流。 RefCount 还给数据流加上引用计数语义，订阅时引用计数器加一，取消订阅时引用计数器减一，订阅者都取消订阅时数据流自动销毁。spa

RefCount

  • RxNET
var period = TimeSpan.FromSeconds(1);
var observable = Observable.Interval(period)
.Do(l => Console.WriteLine("Publishing {0}", l)) //side effect to show it is running
.Publish()
.RefCount();
//observable.Connect(); Use RefCount instead now 
Console.WriteLine("Press any key to subscribe");
Console.ReadKey();
var subscription = observable.Subscribe(i => Console.WriteLine("subscription : {0}", i));
Console.WriteLine("Press any key to unsubscribe.");
Console.ReadKey();
subscription.Dispose();
Console.WriteLine("Press any key to exit.");
Console.ReadKey();
/*
Press any key to subscribe
Press any key to unsubscribe.
Publishing 0
subscription : 0
Publishing 1
subscription : 1
Publishing 2
subscription : 2
Press any key to exit.
*/
  • RxJava
val cold = Observable.interval(200, TimeUnit.MILLISECONDS).publish().refCount()
var s1 = cold.dump("First")
Thread.sleep(500)
val s2 = cold.dump("Second")
Thread.sleep(500)
println("Dispose Second")
s2.dispose()
Thread.sleep(500)
println("Dispose First")
s1.dispose()
println("First connection again")
Thread.sleep(500)
s1 = cold.dump("First")
readLine()
s1.dispose()
/*
First: onNext: 0
First: onNext: 1
First: onNext: 2
Second: onNext: 2
First: onNext: 3
Second: onNext: 3
Dispose Second
First: onNext: 4
First: onNext: 5
First: onNext: 6
Dispose First
First connection again
First: onNext: 0
First: onNext: 1
First: onNext: 2
...
*/

Replay / Cache

ReactiveX - Replay operator Reactive Extensions再入門 その３８「ColdからHotへ！その他のPublish系メソッド２」3d

Replay 给热数据流加上 Replay 语义，即缓存全部的数据，使后来的订阅者也能观察到订阅以前所发送的数据。 Replay 能够指定缓冲区的大小。code

Replay

  • RxNET
Console.WriteLine(MethodBase.GetCurrentMethod().Name);
var hot = Observable.Interval(TimeSpan.FromSeconds(1))
.Take(3)
.Publish();
hot.Connect();
Thread.Sleep(TimeSpan.FromSeconds(1.5)); //Run hot and ensure a value is lost.
var observable = hot.Replay();
observable.Connect();
observable.Subscribe(i => Console.WriteLine("first subscription : {0}", i));
Thread.Sleep(TimeSpan.FromSeconds(1.5));
observable.Subscribe(i => Console.WriteLine("second subscription : {0}", i));
Console.ReadKey();
observable.Subscribe(i => Console.WriteLine("third subscription : {0}", i));
Console.ReadKey();
/*
first subscription : 1
second subscription : 1
first subscription : 2
second subscription : 2
third subscription : 1
third subscription : 2
*/
  • RxJava
val cold = Observable.interval(200, TimeUnit.MILLISECONDS).replay()
cold.connect()
println("Subscribe first")
val s1 = cold.dump("First")
Thread.sleep(700)
println("Subscribe second")
val s2 = cold.dump("Second")
Thread.sleep(500)
readLine()
s1.dispose()
s2.dispose()
/*
Subscribe first
First: onNext: 0
First: onNext: 1
First: onNext: 2
Subscribe second
Second: onNext: 0
Second: onNext: 1
Second: onNext: 2
First: onNext: 3
Second: onNext: 3
First: onNext: 4
Second: onNext: 4
...
*/
val source = Observable.interval(1000, TimeUnit.MILLISECONDS)
    .take(5)
    .replay(2)
source.connect()
Thread.sleep(4500)
source.dump()
/*
onNext: 2
onNext: 3
onNext: 4
onComplete
*/
val source = Observable.interval(1000, TimeUnit.MILLISECONDS)
    .take(5)
    .replay(2000, TimeUnit.MILLISECONDS)
source.connect()
Thread.sleep(4500)
source.dump()
/*
onNext: 2
onNext: 3
onNext: 4
onComplete
*/
val obs = Observable.interval(100, TimeUnit.MILLISECONDS)
    .take(5)
    .cache()
Thread.sleep(500)
obs.dump("First")
Thread.sleep(300)
obs.dump("Second")
/*
First: onNext: 0
First: onNext: 1
First: onNext: 2
Second: onNext: 0
Second: onNext: 1
Second: onNext: 2
First: onNext: 3
Second: onNext: 3
First: onNext: 4
Second: onNext: 4
First: onComplete
Second: onComplete
*/
val obs = Observable.interval(100, TimeUnit.MILLISECONDS)
    .take(5)
    .doOnNext { println(it) }
    .cache()
    .doOnSubscribe { println("Subscribed") }
    .doOnDispose { println("Disposed") }
val subscription = obs.subscribe()
Thread.sleep(150)
subscription.dispose()
/*
Subscribed
0
Disposed
1
2
3
4
*/
  • RxSwift

RxSwift: share vs replay vs shareReplay

let intSequence = Observable<Int>.interval(1, scheduler: MainScheduler.instance)
    .replay(5)
_ = 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)") })
}
/*
Subscription 1:, Event: 0 (after 3 secs)
Subscription 2:, Event: 0 (after 4 secs)
Subscription 1:, Event: 1 (after 4 secs)
Subscription 2:, Event: 1 (after 4 secs)
Subscription 1:, Event: 2 (after 5 secs)
Subscription 2:, Event: 2 (after 5 secs)
Subscription 1:, Event: 3 (after 6 secs)
Subscription 2:, Event: 3 (after 6 secs)
Subscription 1:, Event: 4 (after 7 secs)
Subscription 2:, Event: 4 (after 7 secs)
Subscription 3:, Event: 0 (after 8 secs)
Subscription 3:, Event: 1 (after 8 secs)
Subscription 3:, Event: 2 (after 8 secs)
Subscription 3:, Event: 3 (after 8 secs)
Subscription 3:, Event: 4 (after 8 secs)
Subscription 1:, Event: 5 (after 9 secs)
Subscription 2:, Event: 5 (after 9 secs)
Subscription 3:, Event: 5 (after 9 secs)
...
*/
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