App crashed When updating 2nd version from AppStore but working fine on first download

Hello Everyone,

I am working on the 2nd version of an ios app and it compleated sucessfully and it is published in appstore. the problem is that when the existing user update the app to 2nd version it crashed. But it is working fine when downloaded from appstore after uninstalling the older version. i am not using coredata in my app. only use NSUserDefaults. anyone know about this problem please help me.

Did you make any changes to the items that you are storing in NSUserDefaults? If you changed the attributes of an object that you save, then reading that object in version 2 of your app will have a problem if the object has originally been saved in version 1.