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# save(to:for:completionHandler:)

Saves document data to the specified location in the application sandbox.

```
func save(to url: URL, for saveOperation: UIDocument.SaveOperation, completionHandler: (@Sendable (Bool) -> Void)? = nil)
```

## Parameters

`url`

The file URL identifying the location in the application sandbox to write the document data to. Typically, this is the URL obtained from the [`fileURL`](/documentation/UIKit/UIDocument/fileURL) property.

`saveOperation`

A constant that indicates whether the document file is being written the first time or whether it is being overwritten. See [`UIDocument.SaveOperation`](/documentation/UIKit/UIDocument/SaveOperation) for details.

`completionHandler`

A block with code that is executed when the save operation concludes. The block returns no value and has one parameter:

- `success`: <doc://com.apple.documentation/documentation/Swift/true> if the save operation succeeds, otherwise <doc://com.apple.documentation/documentation/Swift/false>.

    This block is invoked on the calling queue.

## Discussion

The default implementation of this method first calls the [`contents(forType:)`](/documentation/UIKit/UIDocument/contents(forType:)) method synchronously on the calling queue to get the document data to save. Then it calls the [`writeContents(_:andAttributes:safelyTo:for:)`](/documentation/UIKit/UIDocument/writeContents(_:andAttributes:safelyTo:for:)) method on a background queue to perform the actual writing of the data to disk.

If you override this method, it’s recommended that you first call the superclass implementation of the method (`super`). If you do not call `super`, you must do two things:

- Call [`performAsynchronousFileAccess(_:)`](/documentation/UIKit/UIDocument/performAsynchronousFileAccess(_:)) to put the save operation on a background queue.
- In the block parameter, implement coordinated writing by using the <doc://com.apple.documentation/documentation/Foundation/NSFileCoordinator> class.
- From within the coordinated write, call [`writeContents(_:andAttributes:safelyTo:for:)`](/documentation/UIKit/UIDocument/writeContents(_:andAttributes:safelyTo:for:)).

---

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