如何知道用户是否更新了应用程序或安装了新副本？

I will be sending out an update to my app with a new data structure, therefore if a user is updating my app I need to update their current data. So I was wondering how can I programatically tell if the user updated my app or installed a new copy (if a new copy is installed I don't need to update anything) ?I will be sending out an update to my app with