# SecTransformDataBlock A block used to override the default data handling for a transform. ``` typealias SecTransformDataBlock = (CFTypeRef) -> Unmanaged? ``` ## Parameters `data` The data to be processed. When this block is used to to implement the [`kSecTransformActionProcessData`](/documentation/Security/kSecTransformActionProcessData) action, the data is the input data that is to be processed into the output data. When this block is used to implement the [`kSecTransformActionInternalizeExtraData`](/documentation/Security/kSecTransformActionInternalizeExtraData) action, the data is a that contains the data that needs to be imported. ## Return Value `NULL` for the [`kSecTransformActionInternalizeExtraData`](/documentation/Security/kSecTransformActionInternalizeExtraData) action, the data to be passed to the output attribute for any other action, or a instance on failure. ## Discussion --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)