永久数据仍然导致应用程序崩溃，即使在应用程序更新后

Question

I am using Firebase for my data and using persistence to allow offline viewing of that data. My app is still in beta so I am still finding bugs that crash the app and fixing them but when I push a new update the app still crashes until I delete the app and reinstall a fresh version. For example, I have a list of users. If a user signs up for the app and it gets entered incorrectly in the database, the rest of the app works fine but just the users menu where the user can see all of the users crashes. So I fix the error and push out a new version on TestFlight but that users view still crashes even though I fixed the issue. It's not until I delete the app and reinstall that it works.

I know this is due to my having persistence turned on but is there a way to programmatically clear what is in memory only when a new version of the app is installed? I don't want to have to tell all of my testers to delete and reinstall every time a bug comes up if I don't have to.

Answer 1

It sounds like you changed the database/content structure in the new version. So read/write to the old (persisted) database/content failed. Normally you have to define migration rules that convert your database/content from an old version to the new one, so you can use it after the update without problems. I do not know Firebase, so I can't help you with it.

Another alternative is to remove the persisted data whenever you have an incompatible new version and start with a cleanup directly after the update. Assuming that the already launched app has the version 1.0.0 you can do something like that early in your app flow:

NSString *lastKnownVersion = [[NSUserDefaults standardUserDefaults] stringForKey:@"LastKnownAppVersion"];
NSString *currentVersion = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleVersion"]
if (!lastKnownVersion || [currentVersion compare:newVersion options:NSNumericSearch]==NSOrderedAscending) {
    if (!lastKnownVersion) {
        // first start after update from version 1.0.0 (or lower) to a larger version
        // cleanup code here
    } else if ([lastKnownVersion compare:@"2.0.0" options:NSNumericSearch]==NSOrderedAscending) {
        // first start after update from version 1.0.1 up to 2.0.0 to a larger version
        // cleanup code here
    } // ... add more versions that need a legacy handling
    [[NSUserDefaults standardUserDefaults] setObject:currentVersion forKey:@"LastKnownAppVersion"];
    [[NSUserDefaults standardUserDefaults] synchronize];
}