问题
I thought it's impossible, because all the data store in a sandbox, when user delete the app, all the data should be removed from the device.
But somehow, this happened:
I downloaded a wallpaper app from the appstore.
It's a free app, if you don't pay, you can download limited wallpapers, up to 105.
- I download a wallpaper and save to my album. it's now 1/105.
- I delete the app, and delete the wallpaper in my album.
I turn off the iCloud backup function. OK, It's totally removed from my device, right?
I download it again.
- I enter flight mode, so there is no internet connection.
- I open the app, no wallpaper preview can be download from internet.
But the save count shows 1/105!
I'm not trying to steal their wallpapers, I did not change my wallpaper for 4 months. I just wanna know, how can this app know I saved 1 wallpaper already?
- I delete the app. so it's not store in the app documents or tmp folder.
- I delete the wallpaper in my album, SO it can't get it from an MD5 of my album.
- I am in flight mode, so it can't get it from their server or anywhere on the internet.
Anyone knows where this app stored the save/download count?
回答1:
This is done using the keychain on iOS most likely.
Read up on it here: https://developer.apple.com/library/mac/documentation/security/Reference/keychainservices/Reference/reference.html
来源：https://stackoverflow.com/questions/9180226/how-to-store-local-data-after-user-delete-my-ios-app