I am planning to make my app free with ads but include an option to remove ads. Can I automatically give the add-on to all the previous buyers?
Yes and there’s a few different ways to do it. The path I followed was to release a small update that use
NSUserDefaults to write a bool property when the app was installed. Then, when I distributed the app update with the ads, I’d read if the user had that bool value. If they did, they were a previous owner and I wouldn’t show the ads. If not, they were a new owner and got the ads.
You can do the same thing by having the app set a value on your own server (the app would call your server upon installation with a user-specific string). This would do the same as using
NSUserDefaults except the value is stored on your server and not the user’s device.
There’s a few examples online including how to store the bool value that will stay with the user even if they delete and reinstall the app.