is that possible to implement a backup/restore (with iCloud for example) so that when a user reinstall its app on another device can retrieve some important files ?
Hello.
I already have FileSharing enabled and I can see the files in Itunes. But If I just uninstall the app and reinstall (on the same device or on a different device with the same account), they are not automatically restored.
Files will only be restored if iCloud backup ran since the app was installed and if you reinstall the app from iCloud. I don't think that the data will be kept if you uninstall the app.
It is relevant when you reinstall a device from iCloud. For example when you switch to a new device.
You can use ActivityViewController to let the user upload files to iCloud. You can use DocumentPickerViewController to let the user download a file from iCloud.