Added support for custom functions in combineLatest.

Author: Christopher Grimm

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

@@ -252,6 +252,15 @@ class RxScalaDemo extends JUnitSuite {
     sequenced subscribe {x => println(s"Emitted group: $x")}
   }
 
+  @Test def combineLatestExample() {
+    val first_counter = Observable.interval(250 millis)
+    val second_counter = Observable.interval(550 millis)
+    val combined_counter = first_counter.combineLatest(second_counter,
+      (x: Long, y: Long) => List(x,y)) take 10
+
+    combined_counter subscribe {x => println(s"Emitted group: $x")}
+  }
+
 
   @Test def olympicsExample() {
     val medals = Olympics.mountainBikeMedals.publish

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

@@ -1486,6 +1486,22 @@ trait Observable[+T]
     toScalaObservable[(T, U)](rx.Observable.combineLatest[T, U, (T, U)](this.asJavaObservable, that.asJavaObservable, f))
   }
 
+
+  /**
+   * Combines two observables, emitting some type `R` specified in the function f,
+   * each time an event is received from one of the source observables, where the aggregation
+   * is defined by the given function.
+   *
+   *@param that
+   *           The second source observable.
+   *@param f
+               The function that is used combine the emissions of the two observables.
+   *@return An Observable that combines the source Observables according to the function f.
+   */
+  def combineLatest[U,R](that: Observable[U], f: (T, U) => R): Observable[R] = {
+    toScalaObservable[R](rx.Observable.combineLatest[T, U, R](this.asJavaObservable, that.asJavaObservable, f))
+  }
+
   /**
    * Debounces by dropping all values that are followed by newer values before the timeout value expires. The timer resets on each `onNext` call.
    *