Merge pull request #458 from alanfgn/scala-visitor

Adding visitor pattern in scala

Behavioral/Visitor/scala/Visitor.scala

@@ -0,0 +1,68 @@
+
+trait Element {
+  def accept(visitor: Visitor)
+}
+
+trait Visitor {
+
+  def visitElementA(elementA: ElementA)
+
+  def visitElementB(elementB: ElementB)
+}
+
+
+class ElementA extends Element {
+
+  override def accept(visitor: Visitor): Unit = {
+    visitor.visitElementA(this)
+  }
+
+  def featureOfElementA() = "Feature of element A"
+
+}
+
+class ElementB extends Element {
+
+  override def accept(visitor: Visitor): Unit = {
+    visitor.visitElementB(this)
+  }
+
+  def featureOfElementB() = "Feature of element B"
+
+}
+
+class ConcreteVisitorAlpha extends Visitor {
+
+  override def visitElementA(elementA: ElementA): Unit = {
+    println(f"Concrete Visitor Alpha visiting ${elementA.featureOfElementA()}")
+  }
+
+  override def visitElementB(elementB: ElementB): Unit = {
+    println(f"Concrete Visitor Alpha visiting ${elementB.featureOfElementB()}")
+  }
+}
+
+class ConcreteVisitorBeta extends Visitor {
+
+  override def visitElementA(elementA: ElementA): Unit = {
+    println(f"Concrete Visitor Beta visiting ${elementA.featureOfElementA()}")
+  }
+
+  override def visitElementB(elementB: ElementB): Unit = {
+    println(f"Concrete Visitor Beta visiting ${elementB.featureOfElementB()}")
+  }
+}
+
+
+object VisitorPattern {
+  def main(args: Array[String]): Unit = {
+    val elements = Seq(new ElementA(), new ElementB())
+    val visitors = Seq(new ConcreteVisitorAlpha(), new ConcreteVisitorBeta())
+
+    elements.foreach(element => {
+      visitors.foreach(visitor => {
+        element.accept(visitor)
+      })
+    })
+  }
+}