public enum IosXcodeVersion

Which Xcode the build server compiles an iOS build with.

The constants are the majors a current build server image carries. That domain belongs to the image rather than to this framework, so it moves on its own schedule and this enum can only follow at the pace of a release – which is why leaving the attribute unset is the normal thing to do, and why a version outside this set is still reachable through a plain codename1.arg.ios.xcode_version=<version> line in codenameone_settings.properties. That is not a conflict: an attribute left at DEFAULT writes nothing, so there is no second declaration to clash with.

A minor version is the same story – the builder accepts 27.1 and this cannot spell it. The constants cover the case that is worth type checking, which is naming a whole major the servers do not have.

The pre-26 values this hint once took – 12.4, 11.3 and the Xcode 7 to 10 chain before them – are deliberately absent. They name Xcodes that no current build server installs, so offering them as typed constants would promise a selection that cannot happen. A project still carrying one of them in its properties file keeps whatever it has always built with.