Add a filterByType method to TraversableLikes

src/main/scala/lenthall/collections/EnhancedCollections.scala

@@ -0,0 +1,25 @@
+package lenthall.collections
+
+import scala.collection.TraversableLike
+import scala.collection.generic.CanBuildFrom
+import scala.reflect.ClassTag
+
+object EnhancedCollections {
+
+  /**
+    * After trying and failing to do this myself, I got this to work by copying the answer from here:
+    * https://stackoverflow.com/questions/29886246/scala-filter-by-type
+    */
+  implicit class EnhancedTraversableLike[T2, Repr <: TraversableLike[T2, Repr], That](val traversable: TraversableLike[T2, Repr]) extends AnyVal {
+    /**
+      * Lets you filter a collection by type.
+      * eg.
+      * val xs: Set[Object]
+      * val strings = xs.filterByType[String]
+      */
+    def filterByType[T : ClassTag](implicit bf: CanBuildFrom[Repr, T, That]): That = traversable.collect {
+      case t: T => t
+    }
+  }
+}
+

src/test/scala/lenthall/collections/EnhancedCollectionsSpec.scala

@@ -0,0 +1,22 @@
+package lenthall.collections
+
+import org.scalatest.{FlatSpec, Matchers}
+import lenthall.collections.EnhancedCollections._
+
+class EnhancedCollectionsSpec extends FlatSpec with Matchers {
+  behavior of "EnhancedCollections"
+
+  it should "filter a List by type and return a List" in {
+    val objectList = List("hello", 3, None, "world")
+    val stringList: List[String] = objectList.filterByType[String]
+
+    stringList should be(List("hello", "world"))
+  }
+
+  it should "filter a Set by type and return a Set" in {
+    val objectSet = Set("hello", 3, None, "world")
+    val intSet: Set[Int] = objectSet.filterByType[Int]
+
+    intSet should be(Set(3))
+  }
+}