Add GameObject.SetLayerRecursively (#57)

CHANGELOG.md

@@ -20,6 +20,7 @@
 - X10D.Unity: Added `GameObject.LookAt(GameObject[, Vector3])`
 - X10D.Unity: Added `GameObject.LookAt(Transform[, Vector3])`
 - X10D.Unity: Added `GameObject.LookAt(Vector3[, Vector3])`
+- X10D.Unity: Added `GameObject.SetLayerRecursively(int)`
 - X10D.Unity: Added `GameObject.SetParent(GameObject[, bool])`
 - X10D.Unity: Added `GameObject.SetParent(Transform[, bool])`
 - X10D.Unity: Added `Random.NextColorArgb()`

X10D.Unity.Tests/Assets/Tests/GameObjectTests.cs

@@ -61,6 +61,30 @@ namespace X10D.Unity.Tests
             yield break;
         }
 
+        [UnityTest]
+        public IEnumerator SetLayerRecursively_ShouldSetLayerRecursively()
+        {
+            var parent = new GameObject();
+            var child = new GameObject();
+            var grandChild = new GameObject();
+
+            child.transform.SetParent(parent.transform);
+            grandChild.transform.SetParent(child.transform);
+
+            int layer = LayerMask.NameToLayer("UI");
+            Assert.AreNotEqual(layer, parent.layer);
+            Assert.AreNotEqual(layer, child.layer);
+            Assert.AreNotEqual(layer, grandChild.layer);
+
+            parent.SetLayerRecursively(layer);
+
+            Assert.AreEqual(layer, parent.layer);
+            Assert.AreEqual(layer, child.layer);
+            Assert.AreEqual(layer, grandChild.layer);
+
+            yield break;
+        }
+
         [UnityTest]
         public IEnumerator SetParent_ShouldSetParent()
         {

X10D.Unity/src/GameObjectExtensions.cs

@@ -171,6 +171,44 @@ public static class GameObjectExtensions
         gameObject.transform.LookAt(target, worldUp);
     }
 
+    /// <summary>
+    ///      Sets the new layer of this game object and its children, recursively.
+    /// </summary>
+    /// <param name="gameObject">The game object whose layer, and that of its children recursively, to change.</param>
+    /// <param name="layer">The new layer.</param>
+    /// <exception cref="ArgumentNullException"><paramref name="gameObject" /> is <see langword="null" />.</exception>
+    public static void SetLayerRecursively(this GameObject gameObject, int layer)
+    {
+        if (gameObject == null)
+        {
+            throw new ArgumentNullException(nameof(gameObject));
+        }
+
+        gameObject.layer = layer;
+
+        if (gameObject.transform.childCount == 0)
+        {
+            return;
+        }
+
+        var children = new Stack<Transform>(gameObject.transform.Cast<Transform>());
+        while (children.Count > 0)
+        {
+            Transform child = children.Pop();
+            child.gameObject.layer = layer;
+
+            if (child.childCount <= 0)
+            {
+                continue;
+            }
+
+            foreach (Transform grandChild in child)
+            {
+                children.Push(grandChild);
+            }
+        }
+    }
+
     /// <summary>
     ///     Sets the parent of this game object.
     /// </summary>