---
title: "registerUndo(withTarget:selector:object:)"
framework: foundation
role: symbol
role_heading: Instance Method
path: "foundation/undomanager/registerundo(withtarget:selector:object:)"
---

# registerUndo(withTarget:selector:object:)

Registers the selector of the specified target to implement a single undo operation that the target receives.

## Declaration

```swift
func registerUndo(withTarget target: Any, selector: Selector, object: Any?)
```

## Parameters

- `target`: The target of the undo operation. The undo manager maintains an unowned reference to target to prevent retain cycles.
- `selector`: The selector for the undo operation.
- `object`: The argument sent with the selector. The undo manager maintains a strong reference to anO``bject.

## Discussion

Discussion Use registerUndo(withTarget:selector:object:) to register a selector for an undo operation.  To register a selector on the undo stack, you also need to make the method available to the Objective-C runtime by applying the @objc attribute to the method.  For more on how to create a selector, see Selectors. Calling this method also clears the redo stack. The following example demonstrates how to register and use a selector on the undo stack by modeling a Garden class with two methods: plant(flower:) and pluck(flower:).  The plant(flower:) method removes a flower from the garden while pluck(flower:) adds a flower such that effectively, the two methods are inverse operations of each other.  This inverse quality makes it ideal to register plant(flower:) and pluck(flower:) to be each other’s undo operation. class Garden {     typealias FlowerName = String

var flowers: [FlowerName: Int]     var manager = UndoManager()

init(flowers: [FlowerName: Int]) {         self.flowers = flowers     }     @objc func plant(flower: FlowerName) {         flowers[flower, default: 0] += 1         manager.registerUndo(withTarget: self, selector: #selector(pluck), object: flower)     }     @objc func pluck(flower: FlowerName) {         flowers[flower, default: 0] -= 1         manager.registerUndo(withTarget: self, selector: #selector(plant), object: flower)     } } var garden = Garden(flowers: ["orchid" : 2, "lavender": 1, "violet": 2]) garden.pluck(flower: "orchid") //garden.flowers == ["orchid" : 1, "lavender": 1, "violet": 2] garden.manager.undo() //garden.flowers == ["orchid" : 2, "lavender": 1, "violet": 2] important: This method raises internalInconsistencyException if it’s called when no undo group has been established using beginUndoGrouping(). Undo groups are usually set by default, and you rarely need to create a top-level undo group explicitly.

## See Also

### Related Documentation

- [undoNestedGroup()](foundation/undomanager/undonestedgroup().md)
- [groupingLevel](foundation/undomanager/groupinglevel.md)
- [Introduction to Undo Architecture](apple-archive/documentation/Cocoa/Conceptual/UndoArchitecture.md)

### Registering undo operations

- [registerUndo(withTarget:handler:)](foundation/undomanager/registerundo(withtarget:handler:).md)
- [prepare(withInvocationTarget:)](foundation/undomanager/prepare(withinvocationtarget:).md)