Sometimes luck is with me. A month ago we did a bunch of work on powerOne to get it ready for iOS 7. We haven’t updated the interface yet — that’s still coming — but what we did do is make sure bugs were fixed and added a couple of small features.

While I hadn’t started working on iOS 7 yet what was clear is that any work we did do on it was going to have to be for iOS 7 only. There were just too many changes to also try to support the older operating systems. Because of this we wanted to make sure any remaining, known bugs were resolved for the iOS 4.3 to 6.1 customers who can’t or don’t want to upgrade. We were all ready and we did plenty of testing on iOS 7 as well as the earlier OS versions.

iOS 7 shipped last Wednesday and all was quiet. I upgrades devices and iTunes and XCode just like always.

Thursday night, suddenly, I received three bug reports, all in an area of the app I had tested. In some cases — but not always — an error was appearing when a calculation occurred in RPN input mode. Stuff like 5 ENT 6 + would work correctly and 6 ENT 5 + would fail. I could try things one time and it would work, try other things and come back to the original later and it would fail.

At this point I started to panic. There was no way, with the current version of XCode, to target iOS 6.1 and lower devices exclusively and targeting iOS 7 meant that the entire interface of the app was a mess. Furthermore I leave on Sunday for a business trip and did not have the time to completely re-do the interface before I left, not to mention my nightmare scenario of having to figure out some critical issue while away without a laptop.

So we fixed the bugs Thursday night. I didn’t sleep much that night, rolling options around in my head. The only two I could come up with was ignore the problem and tell customers to use algebraic input mode instead (not much of an option) or hustle everything out for iOS 7 (something I didn’t think possible in less than 48 hours without my designer’s help, who was on deadline).

If I could only get the previous XCode version back!

Friday morning, after a couple of conversations with co-workers on the topic, I realized I could get the previous version of XCode back. Time Machine to the rescue!

I’ve had Time Machine backing up my Mac for years now and never once needed to use it. (I also have it backed up to the cloud with CrashPlan.) I was able to recover the previous version of XCode, open powerOne in it, do some testing and submit the fixes to the app store.

I feel lucky this time.