Added Value Change Listeners

Author: ZeroMemes

src/main/java/clientapi/value/IValue.java

@@ -48,6 +48,13 @@ public interface IValue<T> extends Nameable, Describable, Identifiable, IValueHo
      */
     void setValue(T value);
 
+    /**
+     * Adds a change listener to this value
+     *
+     * @param listener The change listener
+     */
+    void addChangeListener(ValueChangeListener<T> listener);
+
     /**
      * Intended to be used with flatMap() to flatten the IValue tree recursively
      * @param value the root node of the tree

src/main/java/clientapi/value/Value.java

@@ -47,6 +47,11 @@ public class Value<T> implements IValue<T> {
      */
     private final Map<String, IValue> valueCache = new HashMap<>();
 
+    /**
+     * A list of all of the {@code ValueChangeListeners} waiting for this value to change
+     */
+    private final List<ValueChangeListener<T>> valueChangeListeners = new ArrayList<>();
+
     /**
      * Name of the Value
      */
@@ -117,9 +122,17 @@ public T getValue() {
 
     @Override
     public void setValue(T value) {
+        // Notify all of the change listeners of the new change of state
+        this.valueChangeListeners.forEach(listener -> listener.onValueChanged(this, this.getValue(), value));
+        // Pass the new value to the change function
         this.mutable.accept(value);
     }
 
+    @Override
+    public void addChangeListener(ValueChangeListener<T> listener) {
+        this.valueChangeListeners.add(listener);
+    }
+
     @Override
     public final String getName() {
         return this.name;

src/main/java/clientapi/value/ValueChangeListener.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2018 ImpactDevelopment
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package clientapi.value;
+
+/**
+ * @author Brady
+ * @since 5/31/2018 3:02 PM
+ */
+@FunctionalInterface
+public interface ValueChangeListener<T> {
+
+    void onValueChanged(Value<T> value, T oldValue, T newValue);
+}