I got this error despite documentation saying it exits:
https://developer.apple.com/documentation/foundation/urlresourcevalues/tagnames
I'm building for iPadOS 26.2
Tag names are not available on iOS. Xcode does a pretty good job of explaining that. Consider this snippet:
let values = try url.resourceValues(forKeys: [.tagNamesKey])
// ^ 'tagNamesKey' is unavailable in iOS
let tags = values.tagNames ?? []
That fact is also reflected in the documentation for the tagNamesKey property.
I’m not sure why the documentation for the tagNames property gets this wrong, but it’s definitely a bug in the docs and I encourage you to file it as such.
Please post your bug number, just for the record
Taking a step back, I can see why you might want to work with tags on iOS, so I encourage you to file a separate enhancement request asking for this property to be made available there.
Again, please post your bug number.
Share and Enjoy
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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"