问题
I use iphone UUID for checking user's device is unique.
I already know UUID will be changed when reinstall app.
But, I have a question. Then, when app updated, UUID for my app will be changed?
If UUID changed when app updated, where can I save UUID in iphone permanently(or same effect)?
回答1:
Save out your created UUID into user preferences for the app, which should be backed up - if they restore the app from a backup you'll get back the UUID.
If you want to be even more sure you can get back the same UUID, save the generated UUID into the keychain - the keychain is kept intact even after you delete an app (not sure if that's guaranteed forever but it is the effect).
回答2:
UDID doesn't change,but it's deprecated. Device ID might change. One can use MAC address if wifi is on, which is pretty much given.
来源：https://stackoverflow.com/questions/14699981/iphone-uuid-change-when-app-updated