Version: 2022.3
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Undo

class in UnityEditor

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Description

Lets you register undo operations on specific objects you are about to perform changes on.

The Undo system stores delta changes in the undo stack.

Undo operations automatically combine together based on events. For example, mouse down events split undo groups. Grouped undo operations appear and work as a single undo. To control grouping manually, use Undo.IncrementCurrentGroup.

By default, the name shown in the UI is selected from the actions from the group using a hardcoded ordering of the different kinds of actions. To manually set the name, use Undo.SetCurrentGroupName.

Undo operations store either per property or per object state. They scale well with any Scene size.

The most important operations are outlined below:

Modify a single property:
Undo.RecordObject (myGameObject.transform, "Zero Transform Position");
myGameObject.transform.position = Vector3.zero;

Add a component:
Undo.AddComponent<Rigidbody>(myGameObject);

Create a new GameObject:
var go = new GameObject();
Undo.RegisterCreatedObjectUndo (go, "Created go");

Destroy a GameObject or component:
Undo.DestroyObjectImmediate (myGameObject);

Change transform parenting:
Undo.SetTransformParent (myGameObject.transform, newTransformParent, "Set new parent");

Static Properties

isProcessingReturns true if the editor is currently processing undo or redo operations, false otherwise.
postprocessModificationsCallback that is triggered whenever a new set of property modifications is created.
undoRedoEventCallback that is triggered after any undo or redo event.
undoRedoPerformedCallback that is triggered after an undo or a redo was executed.
willFlushUndoRecordInvoked before the Undo system performs a flush.

Static Methods

AddComponentAdds a component to the game object and registers an undo operation for this action.
ClearAllRemoves all undo and redo operations from respectively the undo and redo stacks.
ClearUndoRemoves all Undo operation for the identifier object registered using Undo.RegisterCompleteObjectUndo from the undo stack.
CollapseUndoOperationsCollapses all undo operation up to group index together into one step.
DestroyObjectImmediateDestroys the object and records an undo operation so that it can be recreated.
FlushUndoRecordObjectsEnsure objects recorded using RecordObject or RecordObjects are registered as an undoable action. In most cases there is no reason to invoke FlushUndoRecordObjects since it's automatically done right after mouse-up and certain other events that conventionally marks the end of an action.
GetCurrentGroupUnity automatically groups undo operations by the current group index.
GetCurrentGroupNameGet the name that will be shown in the UI for the current undo group.
IncrementCurrentGroupUnity automatically groups undo operations by the current group index.
MoveGameObjectToSceneMove a GameObject from its current Scene to a new Scene. It is required that the GameObject is at the root of its current Scene.
PerformRedoPerform an Redo operation.
PerformUndoPerform an Undo operation.
RecordObjectRecords any changes done on the object after the RecordObject function.
RecordObjectsRecords multiple undoable objects in a single call. This is the same as calling Undo.RecordObject multiple times.
RegisterChildrenOrderUndoStores a copy of the order of the object's children on the undo stack.
RegisterCompleteObjectUndoStores a copy of the object states on the undo stack.
RegisterCreatedObjectUndoRegisters an undo operation to undo the creation of an object.
RegisterFullObjectHierarchyUndoCopy the states of a hierarchy of objects onto the undo stack.
RegisterImporterUndoCopies the state of the importer for the given asset path.
RevertAllDownToGroupPerforms all undo operations up to the group index without storing a redo operation in the process.
RevertAllInCurrentGroupPerforms the last undo operation but does not record a redo operation.
SetCurrentGroupNameSet the name of the current undo group.
SetSiblingIndexSets the sibling index of transform and records an undo operation.
SetTransformParentSets the parent of transform to the new parent and records an undo operation.

Delegates

PostprocessModificationsDelegate used for postprocessModifications.
UndoRedoCallbackDelegate used for undoRedoPerformed.
UndoRedoEventCallbackDelegate used for undoRedoEvent.
WillFlushUndoRecordDelegate used for willFlushUndoRecord.

Is something described here not working as you expect it to? It might be a Known Issue. Please check with the Issue Tracker at issuetracker.unity3d.com.

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