How do I override a func that is available before iOS 12.0

I cannot reproduce the exact message "Overriding 'value' must be as available as declaration it overrides", both in Xcode 10.3 and 11.

Please show the version of your Xcode, and enough code to reproduce the issue.

I do not believe it is due to the existence of `@available(iOS 12.0, *)`, but generally, overriding `value(forUndefinedKey:)` might not be the right solution to fix `NSUnknownKeyException`.

Please show your code on how you added your property and on how you access it.

Xcode 11 GM 2

@available(iOS 12.0, *) @available(iOSApplicationExtension 12.0, *)
extension MySiriIntent {
    override public func value(forUndefinedKey key: String) -> Any? {
        if key == "myKey" {
          //return an appropriate value for myKey
        }
        return nil
    }
}

(lldb) po [$arg1 name]

NSUnknownKeyException

(lldb) po [$arg1 reason]

'myKey' is an invalid parameter for 'MySiriIntent'. Please make sure that your intent definition file is valid.

Ok, looking closer, I see that I confused the NSUndefinedKeyException with NSUnknownKeyException, so, to your point, may be barking up the wrong tree here.

Does anyone know how iOS handles changes to siriIntent definitions? I've added a property, and now previous versions of the shortcut fail, because an NSUnkownKeyException i raised when trying to access the new property.

Some more details, this happens on a call to INGetIdProperty, which throws the NSUnknownKeyException. Looks like it is fixed in iOS 13, new properties are nil when an older versoin of the intent is loaded.