Unity Editor Tools
Editor Scripting Overview
Editor scripts extend the Unity Editor with custom inspectors, windows, tools, and workflows. All editor code must either live in an Editor/ folder or be wrapped in #if UNITY_EDITOR / #endif -- this ensures editor code is stripped from runtime builds.
Unity 6.3 supports two GUI frameworks for editor extensions:
| Framework | Status | Entry Point |
|---|
| UI Toolkit | Recommended | CreateInspectorGUI() / CreateGUI() returning VisualElement |
| IMGUI | Legacy, fully functional | OnInspectorGUI() / OnGUI() |
Key base classes: Editor, EditorWindow, PropertyDrawer, DecoratorDrawer, ScriptableWizard.
Custom Inspector (Editor)
Derive from Editor, apply [CustomEditor(typeof(TargetType))]. See references/custom-inspectors.md for full guide.
UI Toolkit (Recommended)
[CustomEditor(typeof(MyPlayer))]
public class MyPlayerEditor : Editor
{
public override VisualElement CreateInspectorGUI()
{
VisualElement root = new VisualElement();
var visualTree = Resources.Load("MyPlayerEditor") as VisualTreeAsset;
visualTree.CloneTree(root);
return root;
}
}
When CreateInspectorGUI() is overridden, OnInspectorGUI() is ignored.
IMGUI with SerializedObject Pattern
[CustomEditor(typeof(LookAtPoint))]
[CanEditMultipleObjects]
public class LookAtPointEditor : Editor
{
SerializedProperty lookAtPoint;
void OnEnable() { lookAtPoint = serializedObject.FindProperty("lookAtPoint"); }
public override void OnInspectorGUI()
{
serializedObject.Update();
EditorGUILayout.PropertyField(lookAtPoint);
serializedObject.ApplyModifiedProperties();
}
}
Key Members
| Member | Description |
|---|
target / targets | Inspected object(s) |
serializedObject | SerializedObject for the target(s) |
DrawDefaultInspector() | Renders built-in default inspector |
OnSceneGUI() | Draw interactive Handles in Scene View |
Scene View Integration
public void OnSceneGUI()
{
var t = (LookAtPoint)target;
EditorGUI.BeginChangeCheck();
Vector3 pos = Handles.PositionHandle(t.lookAtPoint, Quaternion.identity);
if (EditorGUI.EndChangeCheck())
{
Undo.RecordObject(target, "Move look-at point");
t.lookAtPoint = pos;
}
}
PropertyDrawer and PropertyAttribute
Customize how serialized fields appear in the Inspector. See references/property-drawers.md for full guide.
1. Define attribute (runtime code, outside Editor folder):
public class MyRangeAttribute : PropertyAttribute
{
public readonly float min, max;
public MyRangeAttribute(float min, float max) { this.min = min; this.max = max; }
}
2. Implement drawer (Editor folder):
[CustomPropertyDrawer(typeof(MyRangeAttribute))]
public class MyRangeDrawer : PropertyDrawer
{
public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
{
MyRangeAttribute range = (MyRangeAttribute)attribute;
if (property.propertyType == SerializedPropertyType.Float)
EditorGUI.Slider(position, property, range.min, range.max, label);
else if (property.propertyType == SerializedPropertyType.Integer)
EditorGUI.IntSlider(position, property, (int)range.min, (int)range.max, label);
}
}
Critical rules: Must be in Editor/ folder. Use EditorGUI (not EditorGUILayout). Use EditorGUI.BeginProperty()/EndProperty() for prefab overrides. Cannot mix UI Toolkit and IMGUI in one drawer.
EditorWindow
Custom dockable editor windows. See references/editor-windows.md for full guide.
Lifecycle: OnEnable -> CreateGUI -> Update -> OnGUI -> OnDisable
public class MyToolWindow : EditorWindow
{
[MenuItem("Tools/My Tool Window")]
public static void ShowWindow()
{
var window = GetWindow<MyToolWindow>();
window.titleContent = new GUIContent("My Tool");
window.minSize = new Vector2(300, 200);
}
public void CreateGUI()
{
rootVisualElement.Add(new Label("Hello from UI Toolkit!"));
rootVisualElement.Add(new Button(() => Debug.Log("Clicked!")) { text = "Click Me" });
}
}
| Static Method | Description |
|---|
GetWindow<T>() | Get existing or create new |
CreateWindow<T>() | Always create new instance |
HasOpenInstances<T>() | Check if open |
| Display Mode | Behavior |
|---|
Show() | Standard dockable |
ShowUtility() | Floating, not dockable |
ShowModal() | Modal dialog |
ShowAsDropDown() | Dropdown popup |
MenuItem
The [MenuItem] attribute converts static methods into menu commands.
[MenuItem("Menu/Path/Item Name", isValidateFunction, priority)]
| Prefix | Placement |
|---|
"Tools/..." | Custom tools menu |
"Assets/..." | Assets menu + Project context menu |
"GameObject/..." | GameObject menu + Hierarchy context menu |
"CONTEXT/ComponentType/..." | Component context menu |
Shortcut modifiers: % = Cmd/Ctrl, # = Shift, & = Alt, ^ = Ctrl (all), _ = no modifier.
// Validation function controls when menu item is enabled
[MenuItem("Tools/Reset Position", true)]
static bool ValidateResetPosition() => Selection.activeTransform != null;
[MenuItem("Tools/Reset Position", false)]
static void ResetPosition()
{
Undo.RecordObject(Selection.activeTransform, "Reset Position");
Selection.activeTransform.position = Vector3.zero;
}
GameObject creation (use priority 10):
[MenuItem("GameObject/Custom/My Object", false, 10)]
static void CreateMyObject(MenuCommand menuCommand)
{
var go = new GameObject("My Object");
GameObjectUtility.SetParentAndAlign(go, menuCommand.context as GameObject);
Undo.RegisterCreatedObjectUndo(go, "Create My Object");
Selection.activeObject = go;
}
Gizmos and Handles
Gizmos -- Visual Debugging in Scene/Game View
All drawing inside OnDrawGizmos() (always) or OnDrawGizmosSelected() (when selected):
void OnDrawGizmos()
{
Gizmos.color = Color.yellow;
Gizmos.DrawWireSphere(transform.position, radius);
}
void OnDrawGizmosSelected()
{
Gizmos.color = Color.red;
Gizmos.DrawSphere(transform.position, radius);
}
Methods: DrawLine, DrawRay, DrawSphere, DrawWireSphere, DrawCube, DrawWireCube, DrawMesh, DrawWireMesh, DrawFrustum, DrawIcon. Properties: color, matrix.
Handles -- Interactive 3D Controls (Editor Only)
Used inside OnSceneGUI() on custom Editors:
[CustomEditor(typeof(CircleLayout))]
public class CircleLayoutEditor : Editor
{
public void OnSceneGUI()
{
var t = (CircleLayout)target;
Handles.color = new Color(1f, 0.8f, 0.4f, 1f);
Handles.DrawWireDisc(t.transform.position, t.transform.up, t.radius);
Handles.Label(t.transform.position, $"Radius: {t.radius:F1}");
EditorGUI.BeginChangeCheck();
float newRadius = Handles.RadiusHandle(Quaternion.identity, t.transform.position, t.radius);
if (EditorGUI.EndChangeCheck())
{
Undo.RecordObject(t, "Change Radius");
t.radius = newRadius;
}
}
}
Methods: PositionHandle, RotationHandle, ScaleHandle, FreeMoveHandle, RadiusHandle, DrawLine, DrawWireDisc, Label, BeginGUI/EndGUI. Properties: color, matrix.
SerializedObject Pattern
The standard way to edit properties in editor scripts. Provides automatic Undo, multi-object editing, and prefab override tracking.
Three-step pattern:
serializedObject.Update(); // 1. Sync from target
EditorGUILayout.PropertyField(serializedObject.FindProperty("myField")); // 2. Draw/modify
serializedObject.ApplyModifiedProperties(); // 3. Apply with undo
| Member | Description |
|---|
Update() | Refresh from target |
ApplyModifiedProperties() | Commit changes with undo |
FindProperty(string) | Get SerializedProperty by name |
GetIterator() | Iterate all properties |
targetObject / targetObjects | Inspected object(s) |
hasModifiedProperties | True when unapplied changes exist |
For multi-object editing: add [CanEditMultipleObjects] and always use SerializedProperty instead of target.
AssetDatabase
Programmatic asset access in editor scripts.
// Create
var data = ScriptableObject.CreateInstance<MyData>();
AssetDatabase.CreateAsset(data, "Assets/Data/MyData.asset");
AssetDatabase.SaveAssets();
// Load
var loaded = AssetDatabase.LoadAssetAtPath<MyData>("Assets/Data/MyData.asset");
// Find by type
string[] guids = AssetDatabase.FindAssets("t:MyData");
foreach (string guid in guids)
{
string path = AssetDatabase.GUIDToAssetPath(guid);
var asset = AssetDatabase.LoadAssetAtPath<MyData>(path);
}
// Other operations
AssetDatabase.GetAssetPath(myObject);
AssetDatabase.DeleteAsset("Assets/Data/OldData.asset");
AssetDatabase.Refresh();
Key methods: CreateAsset, LoadAssetAtPath<T>, FindAssets, GetAssetPath, AssetPathToGUID/GUIDToAssetPath, SaveAssets, Refresh, DeleteAsset, CopyAsset, MoveAsset, RenameAsset, ImportAsset.
Common Patterns
// Editor-only guard
#if UNITY_EDITOR
using UnityEditor;
// editor code
#endif
// Change detection
EditorGUI.BeginChangeCheck();
// ... controls ...
if (EditorGUI.EndChangeCheck()) { Undo.RecordObject(target, "Change"); }
// ScriptableObject creation menu
[CreateAssetMenu(fileName = "NewConfig", menuName = "Game/Config Data", order = 1)]
public class ConfigData : ScriptableObject { public float moveSpeed = 5f; }
// Default inspector + extras
[CustomEditor(typeof(MyComponent))]
public class MyComponentEditor : Editor
{
public override void OnInspectorGUI()
{
DrawDefaultInspector();
if (GUILayout.Button("Do Something")) { ((MyComponent)target).DoSomething(); }
}
}
Anti-Patterns
| Anti-Pattern | Problem | Fix |
|---|
Editing target without Undo | No undo, no dirty flag | Use SerializedObject or Undo.RecordObject() |
target with [CanEditMultipleObjects] | Only modifies first object | Use SerializedProperty |
Editor code outside Editor/ without #if UNITY_EDITOR | Build failures | Use Editor/ folder or preprocessor guard |
EditorGUILayout in PropertyDrawer | Not supported | Use EditorGUI with Rect |
Missing serializedObject.Update() | Stale data | Always call before reading |
Missing ApplyModifiedProperties() | Changes lost | Always call after modifications |
| Mixing UI Toolkit + IMGUI in one PropertyDrawer | Not supported | Choose one framework |
Missing Undo.RegisterCreatedObjectUndo() | Cannot undo creation | Always register new objects |
Missing GameObjectUtility.SetParentAndAlign() | Wrong hierarchy parenting | Use in GameObject menu items |
Heavy work in OnInspectorGUI()/OnGUI() | Lag (called many times/frame) | Cache in OnEnable() |
Key API Quick Reference
Editor: [CustomEditor(typeof(T))], [CanEditMultipleObjects]
CreateInspectorGUI(), OnInspectorGUI(), OnSceneGUI()
DrawDefaultInspector(), target, targets, serializedObject
EditorWindow: GetWindow<T>(), CreateWindow<T>(), CreateGUI(), OnGUI()
rootVisualElement, titleContent, Show/ShowUtility/ShowModal
PropertyDrawer: [CustomPropertyDrawer(typeof(T))]
CreatePropertyGUI(), OnGUI(rect,prop,label), GetPropertyHeight()
attribute, fieldInfo, preferredLabel
SerializedObject: Update(), ApplyModifiedProperties(), FindProperty()
MenuItem: [MenuItem("Path", validate, priority)], % # & ^ _ shortcuts
Gizmos: DrawLine/Sphere/WireSphere/Cube/WireCube/Ray/Mesh/Icon, color, matrix
Handles: PositionHandle/RotationHandle/ScaleHandle/FreeMoveHandle/RadiusHandle
DrawLine/DrawWireDisc/Label, BeginGUI/EndGUI, color, matrix
AssetDatabase: CreateAsset, LoadAssetAtPath<T>, FindAssets, SaveAssets, Refresh
Related Skills
- unity-foundations -- Project structure, assembly definitions, Editor folders
- unity-scripting -- MonoBehaviour lifecycle, SerializeField, ScriptableObject
- unity-ui -- UI Toolkit fundamentals, VisualElement, UXML, USS
Additional Resources