问题:

My iOS app is nearly complete, but I read about swift's performance improvements in xcode 6.3 and wanted to take advantage. If I use the latest xcode but compile my app for iOS 8.1 (publicly available) will I have any problems submitting my app?

回答1:

App needs to be compiled with release version of Xcode.

I was already using Xcode 6.3 Beta, and it doesn't let me submit to the Appstore.

I would not recommend using the beta version of Xcode if you plan to release your app soon.

EDIT: You should be able to use GM version.

回答2:

I won't swear to this time, but in the past Apple has always required that submissions be compiled wit the most recent released (not beta) tool chain

The only exceptions have been to allow an older tool chain to be used for a brief period after a release (a few months) and to allow a beta tool chain to be used for early submissions aimed at major new iOS releases(7.0, 8.0, not 8.1)