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# dataSource

The object that provides the data displayed by the receiver.

```
weak var dataSource: (any NSOutlineViewDataSource)? { get set }
```

## Discussion

The object must implement the appropriate methods of [`NSOutlineViewDataSource`](/documentation/AppKit/NSOutlineViewDataSource). Note that in versions of macOS prior to v10.12, the outline view did not retain the data source in a managed memory environment.

Setting the data source invokes [`tile()`](/documentation/AppKit/NSTableView/tile()).

If the data source doesn’t respond to all of the [`outlineView(_:child:ofItem:)`](/documentation/AppKit/NSOutlineViewDataSource/outlineView(_:child:ofItem:)), [`outlineView(_:isItemExpandable:)`](/documentation/AppKit/NSOutlineViewDataSource/outlineView(_:isItemExpandable:)), [`outlineView(_:numberOfChildrenOfItem:)`](/documentation/AppKit/NSOutlineViewDataSource/outlineView(_:numberOfChildrenOfItem:)), and [`outlineView(_:objectValueFor:byItem:)`](/documentation/AppKit/NSOutlineViewDataSource/outlineView(_:objectValueFor:byItem:)) methods, an <doc://com.apple.documentation/documentation/Foundation/NSExceptionName/internalInconsistencyException> may be raised.

## See Also

[Drag and Drop](/documentation/AppKit/drag-and-drop)

Support the direct manipulation of your app’s content using drag and drop.

[Outline View](/documentation/AppKit/outline-view)

Display a list-based interface for hierarchical data, where each level of hierarchy is indented from the previous one.


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