title: In-App-Purchase Bug
body: <p>I'm developing an iOS application in which users can buy an extra feature through an in app purchase. I have gotten the in app purchasing and restoring the purchases working correctly, where I save a <code>boolean</code> to the <code>NSUserDefaults</code> saying whether they have successfully bought and or restored the purchase.</p>
  
  <p>However there is a bug where if User 1 buys the in app purchase on their phone, then logs into the App Store on User 2's phone and restores purchases. Then logs out again and allows User 2 to log back in, it means User 2 still has that in app purchase unlocked for free as the <code>boolean</code> in <code>NSUserDefaults</code> is still set to true.</p>
  
  <p>I'm trying to find a way to query the user's App Store email or another way to check if the user's App Store email is the same as the one they bought the purchase under. But this needs to be done locally as the user could use this feature when they don't have any internet connection.</p>
  
  <p>Does anyone have any suggestions of how I can do this or any better practices?</p>
  
  <p>Thanks </p>