Merge pull request #1124 from zsxwing/scala-lift

Add lift to rxscala

Author: benjchristensen

language-adaptors/rxjava-scala/src/examples/scala/rx/lang/scala/examples/RxScalaDemo.scala

@@ -645,4 +645,67 @@ class RxScalaDemo extends JUnitSuite {
     val o : Observable[String] = List("alice", "bob", "carol").toObservable
     assertEquals(List("alice", "bob", "carol"), o.retry(3).toBlockingObservable.toList)
   }
+
+  @Test def liftExample1(): Unit = {
+    // Add "No. " in front of each item
+    val o = List(1, 2, 3).toObservable.lift {
+      subscriber: Subscriber[String] =>
+        Subscriber[Int](
+          subscriber,
+          (v: Int)  => subscriber.onNext("No. " + v),
+          e => subscriber.onError(e),
+          () => subscriber.onCompleted
+        )
+    }.toBlockingObservable.toList
+    println(o)
+  }
+
+  @Test def liftExample2(): Unit = {
+    // Split the input Strings with " "
+    val splitStringsWithSpace = (subscriber: Subscriber[String]) => {
+      Subscriber[String](
+        subscriber,
+        (v: String) => v.split(" ").foreach(subscriber.onNext(_)),
+        e => subscriber.onError(e),
+        () => subscriber.onCompleted
+      )
+    }
+
+    // Convert the input Strings to Chars
+    val stringsToChars = (subscriber: Subscriber[Char]) => {
+      Subscriber[String](
+        subscriber,
+        (v: String) => v.foreach(subscriber.onNext(_)),
+        e => subscriber.onError(e),
+        () => subscriber.onCompleted
+      )
+    }
+
+    // Skip the first n items. If the length of source is less than n, throw an IllegalArgumentException
+    def skipWithException[T](n: Int) = (subscriber: Subscriber[T]) => {
+      var count = 0
+      Subscriber[T](
+        subscriber,
+        (v: T) => {
+          if (count >= n) subscriber.onNext(v)
+          count += 1
+        },
+        e => subscriber.onError(e),
+        () => if (count < n) subscriber.onError(new IllegalArgumentException("There is no enough items")) else subscriber.onCompleted
+      )
+    }
+
+    val o = List("RxJava – Reactive Extensions for the JVM").toObservable
+      .lift(splitStringsWithSpace)
+      .map(_.toLowerCase)
+      .lift(stringsToChars)
+      .filter(_.isLetter)
+      .lift(skipWithException(100))
+    try {
+      o.toBlockingObservable.toList
+    }
+    catch {
+      case e: IllegalArgumentException => println("IllegalArgumentException from skipWithException")
+    }
+  }
 }

language-adaptors/rxjava-scala/src/main/scala/rx/lang/scala/JavaConversions.scala

@@ -54,4 +54,12 @@ object JavaConversions {
       val asJavaObservable = observable
     }
   }
+
+  implicit def toJavaOperator[T, R](operator: Subscriber[R] => Subscriber[T]): rx.Observable.Operator[R, T] = {
+    new rx.Observable.Operator[R, T] {
+      override def call(subscriber: rx.Subscriber[_ >: R]): rx.Subscriber[_ >: T] = {
+        toJavaSubscriber[T](operator(toScalaSubscriber[R](subscriber)))
+      }
+    }
+  }
 }

language-adaptors/rxjava-scala/src/main/scala/rx/lang/scala/Observable.scala

@@ -2057,7 +2057,28 @@ trait Observable[+T]
    * @see [[Observable.first]]
    */
   def head: Observable[T] = first
-  
+
+  /**
+   * Returns an Observable that emits all items except the first one, or raises an `UnsupportedOperationException`
+   * if the source Observable is empty.
+   *
+   * @return an Observable that emits all items except the first one, or raises an `UnsupportedOperationException`
+   *         if the source Observable is empty.
+   */
+  def tail: Observable[T] = {
+    lift {
+      (subscriber: Subscriber[T]) => {
+        var isFirst = true
+        Subscriber[T](
+          subscriber,
+          (v: T) => if(isFirst) isFirst = false else subscriber.onNext(v),
+          e => subscriber.onError(e),
+          () => if(isFirst) subscriber.onError(new UnsupportedOperationException("tail of empty Observable")) else subscriber.onCompleted
+        )
+      }
+    }
+  }
+
   /**
    * Returns an Observable that emits the last item emitted by the source Observable or notifies observers of
    * an `NoSuchElementException` if the source Observable is empty.
@@ -2537,6 +2558,23 @@ trait Observable[+T]
     toScalaObservable[util.Map[K, V]](o).map(m => mapFactory() ++ m.toMap)
   }
 
+  /**
+   * Lift a function to the current Observable and return a new Observable that when subscribed to will pass
+   * the values of the current Observable through the function.
+   * <p>
+   * In other words, this allows chaining Observers together on an Observable for acting on the values within
+   * the Observable.
+   * {{{
+   * observable.map(...).filter(...).take(5).lift(new ObserverA()).lift(new ObserverB(...)).subscribe()
+   * }}}
+   *
+   * @param operator
+   * @return an Observable that emits values that are the result of applying the bind function to the values
+   *         of the current Observable
+   */
+  def lift[R](operator: Subscriber[R] => Subscriber[T]): Observable[R] = {
+    toScalaObservable(asJavaObservable.lift(toJavaOperator[T, R](operator)))
+  }
 }
 
 /**

language-adaptors/rxjava-scala/src/main/scala/rx/lang/scala/Subscriber.scala

@@ -49,4 +49,14 @@ object Subscriber extends ObserverFactoryMethods[Subscriber] {
       override def onCompleted(): Unit = c()
     })
   }
+
+  def apply[T](subscriber: Subscriber[_], onNext: T => Unit, onError: Throwable => Unit, onCompleted: () => Unit): Subscriber[T] = {
+    val n = onNext; val e = onError; val c = onCompleted
+    // Java calls XXX; Scala receives XXX.
+    Subscriber(new rx.Subscriber[T](subscriber.asJavaSubscriber) {
+      override def onNext(value: T): Unit = n(value)
+      override def onError(error: Throwable): Unit = e(error)
+      override def onCompleted(): Unit = c()
+    })
+  }
 }

language-adaptors/rxjava-scala/src/test/scala/rx/lang/scala/CompletenessTest.scala

@@ -79,6 +79,7 @@ class CompletenessTest extends JUnitSuite {
       "firstOrDefault(T)" -> "firstOrElse(=> U)",
       "firstOrDefault(Func1[_ >: T, Boolean], T)" -> "[use `.filter(condition).firstOrElse(default)`]",
       "groupBy(Func1[_ >: T, _ <: K], Func1[_ >: T, _ <: R])" -> "[use `groupBy` and `map`]",
+      "lift(Operator[_ <: R, _ >: T])" -> "lift(Subscriber[R] => Subscriber[T])",
       "mapMany(Func1[_ >: T, _ <: Observable[_ <: R]])" -> "flatMap(T => Observable[R])",
       "mapWithIndex(Func2[_ >: T, Integer, _ <: R])" -> "[combine `zipWithIndex` with `map` or with a for comprehension]",
       "onErrorResumeNext(Func1[Throwable, _ <: Observable[_ <: T]])" -> "onErrorResumeNext(Throwable => Observable[U])",
@@ -89,16 +90,28 @@ class CompletenessTest extends JUnitSuite {
       "parallel(Func1[Observable[T], Observable[R]], Scheduler)" -> "parallel(Observable[T] => Observable[R], Scheduler)",
       "reduce(Func2[T, T, T])" -> "reduce((U, U) => U)",
       "reduce(R, Func2[R, _ >: T, R])" -> "foldLeft(R)((R, T) => R)",
+      "retry()" -> "retry()",
       "scan(Func2[T, T, T])" -> unnecessary,
       "scan(R, Func2[R, _ >: T, R])" -> "scan(R)((R, T) => R)",
       "skip(Int)" -> "drop(Int)",
+      "skip(Long, TimeUnit)" -> "drop(Duration)",
+      "skip(Long, TimeUnit, Scheduler)" -> "drop(Duration, Scheduler)",
       "skipWhile(Func1[_ >: T, Boolean])" -> "dropWhile(T => Boolean)",
       "skipWhileWithIndex(Func2[_ >: T, Integer, Boolean])" -> unnecessary,
       "startWith(Iterable[T])" -> "[unnecessary because we can just use `++` instead]",
+      "skipLast(Int)" -> "dropRight(Int)",
+      "skipLast(Long, TimeUnit)" -> "dropRight(Duration)",
+      "skipLast(Long, TimeUnit, Scheduler)" -> "dropRight(Duration, Scheduler)",
       "takeFirst()" -> "first",
       "takeFirst(Func1[_ >: T, Boolean])" -> commentForFirstWithPredicate,
       "takeLast(Int)" -> "takeRight(Int)",
       "takeWhileWithIndex(Func2[_ >: T, _ >: Integer, Boolean])" -> "[use `.zipWithIndex.takeWhile{case (elem, index) => condition}.map(_._1)`]",
+      "timeout(Func0[_ <: Observable[U]], Func1[_ >: T, _ <: Observable[V]], Observable[_ <: T])" -> "timeout(() => Observable[U], T => Observable[V], Observable[O])",
+      "timeout(Func1[_ >: T, _ <: Observable[V]], Observable[_ <: T])" -> "timeout(() => Observable[U], T => Observable[V])",
+      "timeout(Long, TimeUnit, Observable[_ <: T])" -> "timeout(Duration, Observable[U])",
+      "timeout(Long, TimeUnit, Observable[_ <: T], Scheduler)" -> "timeout(Duration, Observable[U], Scheduler)",
+      "timer(Long, Long, TimeUnit)" -> "timer(Duration, Duration)",
+      "timer(Long, Long, TimeUnit, Scheduler)" -> "timer(Duration, Duration, Scheduler)",
       "toList()" -> "toSeq",
       "toSortedList()" -> "[Sorting is already done in Scala's collection library, use `.toSeq.map(_.sorted)`]",
       "toSortedList(Func2[_ >: T, _ >: T, Integer])" -> "[Sorting is already done in Scala's collection library, use `.toSeq.map(_.sortWith(f))`]",

language-adaptors/rxjava-scala/src/test/scala/rx/lang/scala/ObservableTest.scala

@@ -146,16 +146,26 @@ class ObservableTests extends JUnitSuite {
     assertEquals(l2, l1)
   }
 
-  /*
- @Test def testHead() {
-   val observer = mock(classOf[Observer[Int]])
-   val o = Observable().head
-   val sub = o.subscribe(observer)
-
-   verify(observer, never).onNext(any(classOf[Int]))
-   verify(observer, never).onCompleted()
-   verify(observer, times(1)).onError(any(classOf[NoSuchElementException]))
- }
- */
+  @Test def testHead() {
+    val o: Observable[String] = List("alice", "bob", "carol").toObservable.head
+    assertEquals(List("alice"), o.toBlockingObservable.toList)
+  }
+
+  @Test(expected = classOf[NoSuchElementException])
+  def testHeadWithEmptyObservable() {
+    val o: Observable[String] = List[String]().toObservable.head
+    o.toBlockingObservable.toList
+  }
 
+  @Test def testTail() {
+    val o: Observable[String] = List("alice", "bob", "carol").toObservable.tail
+    assertEquals(List("bob", "carol"), o.toBlockingObservable.toList)
+    assertEquals(List("bob", "carol"), o.toBlockingObservable.toList)
+  }
+
+  @Test(expected = classOf[UnsupportedOperationException])
+  def testTailWithEmptyObservable() {
+    val o: Observable[String] = List[String]().toObservable.tail
+    o.toBlockingObservable.toList
+  }
 }