Add stream-substream.md #23461

akka-docs/src/test/scala/docs/stream/SubstreamDocSpec.scala

@@ -0,0 +1,79 @@
+/**
+ * Copyright (C) 2015-2017 Lightbend Inc. <http://www.lightbend.com>
+ */
+package docs.stream
+
+import akka.stream.scaladsl.{ Sink, Source }
+import akka.stream.{ ActorMaterializer, SubstreamCancelStrategy }
+import akka.testkit.AkkaSpec
+
+class SubstreamDocSpec extends AkkaSpec {
+  implicit val materializer = ActorMaterializer()
+
+  "generate substreams by groupBy" in {
+    //#groupBy1
+    val source = Source(1 to 10).groupBy(3, _ % 3)
+    //#groupBy1
+
+    //#groupBy2
+    Source(1 to 10).groupBy(3, _ % 3).to(Sink.ignore).run()
+    //#groupBy2
+
+    //#groupBy3
+    Source(1 to 10)
+      .groupBy(3, _ % 3)
+      .mergeSubstreams
+      .runWith(Sink.ignore)
+    //#groupBy3
+
+    //#groupBy4
+    Source(1 to 10)
+      .groupBy(3, _ % 3)
+      .mergeSubstreamsWithParallelism(2)
+      .runWith(Sink.ignore)
+
+    //concatSubstreams is equivalent to mergeSubstreamsWithParallelism(1)
+    Source(1 to 10)
+      .groupBy(3, _ % 3)
+      .concatSubstreams
+      .runWith(Sink.ignore)
+    //#groupBy4
+  }
+
+  "generate substreams by splitWhen and splitAfter" in {
+    //#splitWhenAfter
+    Source(1 to 10).splitWhen(SubstreamCancelStrategy.drain)(_ == 3)
+
+    Source(1 to 10).splitAfter(SubstreamCancelStrategy.drain)(_ == 3)
+    //#splitWhenAfter
+
+    //#wordCount
+    val text =
+      "This is the first line.\n" +
+        "The second line.\n" +
+        "There is also the 3rd line\n"
+
+    val charCount = Source(text.toList)
+      .splitAfter { _ == '\n' }
+      .filter(_ != '\n')
+      .map(_ ⇒ 1)
+      .reduce(_ + _)
+      .to(Sink.foreach(println))
+      .run()
+    //#wordCount
+  }
+
+  "generate substreams by flatMapConcat and flatMapMerge" in {
+    //#flatMapConcat
+    Source(1 to 2)
+      .flatMapConcat(i ⇒ Source(List.fill(3)(i)))
+      .runWith(Sink.ignore)
+    //#flatMapConcat
+
+    //#flatMapMerge
+    Source(1 to 2)
+      .flatMapMerge(2, i ⇒ Source(List.fill(3)(i)))
+      .runWith(Sink.ignore)
+    //#flatMapMerge
+  }
+}