---
title: "outlineView(_:validateDrop:proposedItem:proposedChildIndex:)"
framework: appkit
role: symbol
role_heading: Instance Method
path: "appkit/nsoutlineviewdatasource/outlineview(_:validatedrop:proposeditem:proposedchildindex:)"
---

# outlineView(_:validateDrop:proposedItem:proposedChildIndex:)

Used by an outline view to determine a valid drop target.

## Declaration

```swift
@MainActor optional func outlineView(_ outlineView: NSOutlineView, validateDrop info: any NSDraggingInfo, proposedItem item: Any?, proposedChildIndex index: Int) -> NSDragOperation
```

## Parameters

- `outlineView`: The outline view that sent the message.
- `info`: An object that contains more information about this dragging operation.
- `item`: The proposed parent.
- `index`: The proposed child location.

## Return Value

Return Value A value that indicates which dragging operation the data source will perform.

## Discussion

Discussion Based on the mouse position, the outline view will suggest a proposed drop location. The data source may “retarget” a drop if desired by calling setDropItem(_:dropChildIndex:) and returning something other than NSDragOperationNone. You may choose to retarget for various reasons (for example, for better visual feedback when inserting into a sorted position). Implementation of this method is optional.

## See Also

### Instance Methods

- [outlineView(_:acceptDrop:item:childIndex:)](appkit/nsoutlineviewdatasource/outlineview(_:acceptdrop:item:childindex:).md)
- [outlineView(_:child:ofItem:)](appkit/nsoutlineviewdatasource/outlineview(_:child:ofitem:).md)
- [outlineView(_:draggingSession:endedAt:operation:)](appkit/nsoutlineviewdatasource/outlineview(_:draggingsession:endedat:operation:).md)
- [outlineView(_:draggingSession:willBeginAt:forItems:)](appkit/nsoutlineviewdatasource/outlineview(_:draggingsession:willbeginat:foritems:).md)
- [outlineView(_:isItemExpandable:)](appkit/nsoutlineviewdatasource/outlineview(_:isitemexpandable:).md)
- [outlineView(_:itemForPersistentObject:)](appkit/nsoutlineviewdatasource/outlineview(_:itemforpersistentobject:).md)
- [outlineView(_:namesOfPromisedFilesDroppedAtDestination:forDraggedItems:)](appkit/nsoutlineviewdatasource/outlineview(_:namesofpromisedfilesdroppedatdestination:fordraggeditems:).md)
- [outlineView(_:numberOfChildrenOfItem:)](appkit/nsoutlineviewdatasource/outlineview(_:numberofchildrenofitem:).md)
- [outlineView(_:objectValueFor:byItem:)](appkit/nsoutlineviewdatasource/outlineview(_:objectvaluefor:byitem:).md)
- [outlineView(_:pasteboardWriterForItem:)](appkit/nsoutlineviewdatasource/outlineview(_:pasteboardwriterforitem:).md)
- [outlineView(_:persistentObjectForItem:)](appkit/nsoutlineviewdatasource/outlineview(_:persistentobjectforitem:).md)
- [outlineView(_:setObjectValue:for:byItem:)](appkit/nsoutlineviewdatasource/outlineview(_:setobjectvalue:for:byitem:).md)
- [outlineView(_:sortDescriptorsDidChange:)](appkit/nsoutlineviewdatasource/outlineview(_:sortdescriptorsdidchange:).md)
- [outlineView(_:updateDraggingItemsForDrag:)](appkit/nsoutlineviewdatasource/outlineview(_:updatedraggingitemsfordrag:).md)
- [outlineView(_:writeItems:to:)](appkit/nsoutlineviewdatasource/outlineview(_:writeitems:to:).md)