问题
Can i save an UUID in an external database in order to check if the user posts his message only one time from his iphone? I have searched and i have found that there is no way to save a NSString value after the app has been deleted. Am i right?
回答1:
When an app is deleted, all of its data is deleted too. You could store the UUID on a remote server, however the iPhone's UUID will be the same regardless of how many times your app is deleted and reinstalled.
Note that this can be a security concern as your remote server may recognize a device which has been wiped and sold.
回答2:
You can save an encrypted NSString in the keychain, and that string will survive the app being deleted. However the user can still securely wipe their phone to clear the keychain. Or log in from multiple iOS devices on their same iTunes account. Or exchange their device for another new device at an Apple store if there is some sort of warranty problem, etc.
来源：https://stackoverflow.com/questions/3868563/uuid-is-unique-iphone