Would the value of NSUserDefaults lost after upgrade the app?
If I delete the app and reinstall it ,and then restore data from Itunes backup, would the value of NSUserDefaults lost?
You don't lose the value of NSUserDefaults when you upgrade the app.
When you delete and reinstall the app, though, you reset all the NSUserDefaults keys, so you can lose data (i.e. your score, etc).
Restoring from backup doesn't lose the NSUserDefaults value, due you've stored the value in iTunes and iTunes is giving you back again that value.
iCloud is the better solution unless you have some reason for not using it, and has the advantage of synchronizing multiple installations by the same user should you so desire.
Related
In ios, If the user backups an application and restores the backup, will the data in NSUserDefault will get persisted? If yes, How to avoid it.
The NSUserDefaults are stored in the backup and therefore will be restored as well.
I'm using [NSUserDefaults standardUserDefaults] for storing application settings.
My questions are:
do those settings are removed on app deletion?
are they kept after an application update (through the
AppStore)?
Because I'm using it to store a password and don't want my users to reset them at each update. Also, I'd like that the only way to reset the password would be to remove the app and re-install it.
Is NSUserDefault the right choice?
Thanks,
Jérémy
Yes, they are removed on app deletion and yes they are kept when an application is updated.
However, you're not advised to store sensitive data in the NSUserDefaults, instead I would look at using the Keychain.
I use NSUserDefaults in my app to allow additional access to my app for my colleagues. They just have to enter the code word in settings and the app is fully opened.
to the point each time I update the app they have to re-enter the code word, so I would say from experience that they are not kept after updates. The values need to be re-entered.
When does data get restored for an app? What if I save data in the app's document directory. Then they sync with iTunes. Now iTunes has a backup. Will that data be populated to another device when they sync that new device to their iTunes or will they just get a clean install of my app? I'm trying to figure out how to keep track of a subscription in app purchase and was wondering if I could keep record in NSUserDefaults or some other local store.
Backups are per-device. So a backup of your iPod will not be restored to your iPhone. In other words, there is no sync.
Many times iTunes fails to create complete backup of all the iPhone data say it be contacts, message, mails etc. This type of problem may occur due to not installing iTunes properly. So, you should check whether iTunes have been installed correctly or not. In case there is no problem with iTunes then it is possible that you are trying to create backup of the files which can not be backed with the help of iTunes. To overcome with this issue you need to make use of iPhone backup application. By using this tool you will be able to prepare backup of all the files within minutes safely.
If the user backs up to iTunes, and then restores their backup to another device (maybe they lost their original iPhone), the contents of the app Documents directory will be put on the new device. Anything in the tmp folder won't be backed up or restored like this, but the Documents folder will.
However, that's not the best way to store the in-app purchase information. You should be storing that on your own server and keeping a count of the number of times the purchased content has been used. Inform the user that they can use it a certain number of times (say three) and after that they will have to buy it again. I'm not exactly sure of any details beyond that (like how to verify their identity) but it should get you started.
I have an app that lets user record their own audio.
By now I'm saving those files into Documents directory.
My question is: if I will release a new version of that app, will user recorded files get deleted?
Is there a better place to store user generated audio files?
Should I use NSUserDefaults for data that stay even after app upgrade?
thx
NSUserDefaults is used for storing settings (objects of Key-Value Coding compliant classes)
Other data such files you should store in Documents folder, wich survive between updates (if you don't delete it yourself, of course :)
Both the Documents directory and NSUserDefaults survive application updates. Choosing which to use depends on the kind of your data.
if I will release a new version of that app, will user recorded files get deleted?
No.
Is there a better place to store user generated audio files?
No.
Should I use NSUserDefaults for data that stay even after app upgrade?
Only if your data is small.
Is this the case? Do NSUserDefaults get reset when you submit an update to an app on the App Store, or are they reset?
My app is crashing when updated but not crashing when downloaded fully - so I'm trying to determine what could possibly be different in the updated session to the freshly downloaded session.
Cheers,
Nick.
They are usually not reset unless the user deletes the app. For basic data, NSUserDefaults is the best way to save data such as preferences, dates, strings etc. If you are looking to save images and files, the file system is a better bet.
I beleive the answer is YES, it will persist. This also fully documented under the Application Directory chapter in the Apple iPhone OS Programming Guide.
Direct answer to the posted question: YES.
Your problem:
Your app gets crashed due to logic issues. Suppose you store an object in defaults and the app checks it's value on launch (or elsewhere). In you update you could change the way it is checked or used, e.g. you expect a value, but the object is nil, or vice versa. This may cause a SIGABRT or EXC_BAD_ACCESS.
If you had CoreData model and you changed something in your model and update, without managing migration, thats probably reason why your app crashes on update...
I have a similar experience. Our app stores a version number in Settings.Bundle/Root.Plist. This gets displayed through the iPhone Settings app. What we find is that on an Install the version number gets loaded from the app bundle - therefore the version number is correct. On an update however the version number doesn't change. This gives the impression the user is running a previous version of the app. We don't have any logic linked to the version number, it's just for display (it could be used by contact centre staff when diagnosing faults).
Our experience is NSUserDefaults doesn't get cleared when a user updates our app, but the Settings display doesn't get updated either.
Be aware of this case, when your app is running in background and you cannot access your stored values in NSUserDefaults:
Eric:
There have been many threads and bugs about this, but it's happening to me again in ios 9. I have an app that launches in the background in response to NSURLSession tasks and content-available pushes. Reproducibly, if I reboot my phone and wait for a background launch of my app to happen, then when I open the app I find that [[NSUserDefaults standardUserDefaults] dictionaryRepresentation] contains all the system values, e.g. AppleITunesStoreItemKinds, etc. but does not contain any of the values I have set. If I force-quit and relaunch the app all of my values come back. Is there any way to avoid it caching the "empty" standardUserDefaults from before the phone is unlocked, or at least to determine when they are messed up and fix them without having to force-quit the app?
Eskimo (eskimo1#apple.com):
The problem here is that NSUserDefaults is ultimately backed by a file in your app’s container and your app’s container is subject to data protection. If you do nothing special then, on iOS 7 and later, your container uses NSFileProtectionCompleteUntilFirstUserAuthentication, a value that’s inherited by the NSUserDefaults backing store, and so you can’t access it prior to first unlock.
IMO the best way around this is to avoid NSUserDefaults for stuff that you rely on in code paths that can execute in the background. Instead store those settings in your own preferences file, one whose data protection you can explicitly manage (in this case that means ‘set to NSFileProtectionNone’).
There are two problems with NSUserDefaults in a data protection context:
Its a fully abstract API: the presence and location of its backing store is not considered part of that API, so you can’t explicitly manage its data protection.
Note On recent versions of OS X NSUserDefaults is managed by a daemon and folks who try to manipulate its backing store directly have run into problems. It’s easy to imagine the same sort of thing coming to iOS at some point.
Even if changing the data protection were possible, NSUserDefaults has no mechanism to classify data based on the context in which you’re using it; it’s an ‘all or nothing’ API. In your case you don’t want to remove protection from all of your user defaults, just those that you need to access in the background before first unlock.
Finally, if any of this data is truly sensitive, you should put it in the keychain. Notably, the keychain does have the ability to set data protection on an item-by-item basis.
Source:
https://webcache.googleusercontent.com/search?q=cache:sR9eZNHpZtwJ:https://forums.developer.apple.com/thread/15685