I figured out how to retrieve first / lastName of a logged in user. Is there a way to get the AppleID too?!
var defaultContainer = CKContainer.defaultContainer()
var publicDatabase = defaultContainer.publicCloudDatabase
defaultContainer.discoverUserInfoWithUserRecordID(recordID, {userInfo, error in
println("firstName: \(userInfo.firstName?) lastName: \(userInfo.lastName?)")
})