# CFNetServiceCreateTXTDataWithDictionary(_:_:) Flattens a set of key/value pairs into a CFDataRef suitable for passing to [`CFNetServiceSetTXTData(_:_:)`](/documentation/CFNetwork/CFNetServiceSetTXTData(_:_:)). ``` func CFNetServiceCreateTXTDataWithDictionary(_ alloc: CFAllocator?, _ keyValuePairs: CFDictionary) -> Unmanaged? ``` ## Parameters `alloc` The allocator to use to allocate memory for the new object. Pass `NULL` or to use the current default allocator. `keyValuePairs` CFDictionaryRef containing the key/value pairs that are to be placed in a TXT record. Each key must be a CFStringRef and each value should be a CFDataRef or a CFStringRef. (See the discussion below for additional information about values that are CFStringRefs.) This function fails if any other data types are provided. The length of a key and its value should not exceed 255 bytes. ## Return Value A CFData object containing the flattened form of `keyValuePairs`, or `NULL` if the dictionary could not be flattened. Ownership follows the [The Create Rule](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFMemoryMgmt/Concepts/Ownership.html#//apple_ref/doc/uid/20001148-103029). ## Discussion This function flattens the key/value pairs in the dictionary specified by `keyValuePairs` into a CFDataRef suitable for passing to [`CFNetServiceSetTXTData(_:_:)`](/documentation/CFNetwork/CFNetServiceSetTXTData(_:_:)). Note that this function is not a general purpose function for flattening CFDictionaryRefs. The keys in the dictionary referenced by `keyValuePairs` must be CFStringRefs and the values must be CFDataRefs. Any values that are CFStringRefs are converted to CFDataRefs representing the flattened UTF-8 bytes of the string. The types of the values are not encoded in the CFDataRefs, so any CFStringRefs that are converted to CFDataRefs remain CFDataRefs when the CFDataRef produced by this function is processed by [`CFNetServiceCreateDictionaryWithTXTData(_:_:)`](/documentation/CFNetwork/CFNetServiceCreateDictionaryWithTXTData(_:_:)). ### Special Considerations This function is thread safe. --- 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)