New observer implementation

src/main/kotlin/oop/Observer2/CategoryObserver.kt

@@ -0,0 +1,11 @@
+package oop.Observer2
+
+class CategoryObserver : Observer<String> {
+  override val list = mutableListOf<Player>()
+
+  override fun onChange(newValue: String){
+    list.forEachIndexed { _, player ->
+      player.notify(newValue)
+    }
+  }
+}

src/main/kotlin/oop/Observer2/Observer.kt

@@ -0,0 +1,6 @@
+package oop.Observer2
+
+interface Observer<T>{
+  val list: MutableList<Player>
+  fun onChange(newValue: T)
+}

src/main/kotlin/oop/Observer2/Player.kt

@@ -0,0 +1,9 @@
+package oop.Observer2
+
+
+data class Player (val name: String,
+                   var currentCategory: String = "history"){
+  fun notify(newCategory: String){
+    println("$name: category changed to $newCategory")
+  }
+}

src/main/kotlin/oop/Observer2/Roulette.kt

@@ -0,0 +1,12 @@
+package oop.Observer2
+
+import kotlin.properties.Delegates
+
+class Roulette{
+
+  var observer: CategoryObserver? = null
+
+  var newCategory: String by Delegates.observable("") { _, _, new ->
+    observer?.onChange(new)
+  }
+}