title: Performing calculations on attributes between entities in core data
body: <p>I am new to xcode/ios etc... and having a little trouble figuring out a problem. I cant seem to figure out how I would retrieve and perform calculations on attributes between entities in core data. Here is an example of what I am trying to do:</p>
  
  <p>My project is a football app that has a one to many relationship. Season to Game (Season has a bunch of games. Season has attributes like teamname and datestart. Game has attributes like passing yards, running yards etc..</p>
  
  <p>How would I be able to calculate something like total passing yards for the whole season (adding all the games passing yards together for that season)?</p>
  
  <p>Thanks for your time.  </p>