Question

I have an iOS app in the AppStore, built with Xcode a while ago, but I am thinking of rewriting it from scratch to iron out some bad decisions and this time use some cross-platform framework such as Appcelerator Titanium or Rhodes to add Android support also.

Is it possible for my current iOS users to seamlessly upgrade to the new version, retaining their userdata (of course a migrator is required in the new app). I think I have to retain some app identifier or other data in the new version.

Or should I create it as totally new app and let the users migrate their data (possibly using the Open in... scheme).
The downside of this is that current users must re-purchase the app, which might drive some of them away.

Answer 1

Is it possible for my current iOS users to seamlessly upgrade to the new version, retaining their userdata (of course a migrator is required in the new app). I think I have to retain some app identifier or other data in the new version.

In principle, it is possible. The fact that you are moving to a different development platform will not affect your ability to access data already stored by the user. In the end, it greatly depends on how you stored that data: if it is through NSUserDefaults, it will be pretty much transparent; if it is in XML/JSON files, you will need to add some XML/JSON parser to you new app (provided Appcelerator Titanium or Rhodes do not already provide one); if it is through sqlite, I know that, e.g., Titanium supports it; if it is through Core Data, maybe you will need to write some kind of converter for the existing data. But, in the end, it is definitely possible.

Or should I create it as totally new app and let the users migrate their data (possibly using the Open in… scheme). The downside of this is that current users must re-purchase the app, which might drive some of them away.

What you should take into account here is how much the new app will differ from the old one. If there is a risk of disappointing your customer base, maybe you can go for a separate version. It is clear that doing so will bother some users that will have paid for the old version. One scheme that has been applied in at least one case I know of is offering the app for free during an initial period. But whether this is sensible or not depends entirely on the prospects of your apps.

Maybe the best approach is striving for a largely improved new version, so that disappointed customers will be the least possible number, and keep the same bundle id for a seamless update.