From 9f5e34c5987d3023ee843456f4f4e9cf1391d154 Mon Sep 17 00:00:00 2001
From: Forrest Li <forrest.li@kitware.com>
Date: Fri, 14 May 2021 17:03:43 -0400
Subject: [PATCH] feat(ClassHierarchy): hierarchy subclasses Array

---
 Sources/Common/Core/ClassHierarchy/index.js | 7 +++++++
 Sources/macro.js                            | 8 +++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)
 create mode 100644 Sources/Common/Core/ClassHierarchy/index.js

diff --git a/Sources/Common/Core/ClassHierarchy/index.js b/Sources/Common/Core/ClassHierarchy/index.js
new file mode 100644
index 00000000000..5e12212f1d4
--- /dev/null
+++ b/Sources/Common/Core/ClassHierarchy/index.js
@@ -0,0 +1,7 @@
+export default class ClassHierarchy extends Array {
+  push(...args) {
+    // no perf issue since args.length should be small
+    const newArgs = args.filter((arg) => !this.includes(arg));
+    return super.push(...newArgs);
+  }
+}
diff --git a/Sources/macro.js b/Sources/macro.js
index 222f3b9ab74..b10446e7b88 100644
--- a/Sources/macro.js
+++ b/Sources/macro.js
@@ -1,4 +1,5 @@
 import vtk from './vtk';
+import ClassHierarchy from './Common/Core/ClassHierarchy';
 
 let globalMTime = 0;
 
@@ -214,7 +215,12 @@ export function obj(publicAPI = {}, model = {}) {
   if (!Number.isInteger(model.mtime)) {
     model.mtime = ++globalMTime;
   }
-  model.classHierarchy = ['vtkObject'];
+
+  if (!('classHierarchy' in model)) {
+    model.classHierarchy = new ClassHierarchy('vtkObject');
+  } else if (!(model.classHierarchy instanceof ClassHierarchy)) {
+    model.classHierarchy = ClassHierarchy.from(model.classHierarchy);
+  }
 
   function off(index) {
     callbacks[index] = null;