# CFXMLParserResolveExternalEntityCallBack Callback function invoked by the parser to notify your application that an external entity has been referenced. ``` typealias CFXMLParserResolveExternalEntityCallBack = (CFXMLParser?, UnsafeMutablePointer?, UnsafeMutableRawPointer?) -> Unmanaged? ``` ## Parameters `parser` The CFXMLParser object making the callback. `extID` The identifier for the external entity. `info` The program-defined context data you specified in the [`CFXMLParserContext`](/documentation/CoreFoundation/CFXMLParserContext) structure when creating the parser. ## Return Value The external entity or `NULL` if it should not be resolved. ## Discussion If this callback is not defined, the parser uses its internal routines to try and resolve the entity. Otherwise, if this callback returns NULL, a place holder for the external entity is inserted into the tree. In this manner, the parser’s client can prevent any external network or file accesses. This callback is optional. --- 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)