title: What's the best choice for this rails model?
body: <p>I have a model called <code>User</code>, and another called <code>Run</code>. Each user have many runs. Duration and distance are attributes of Run.</p>
  
  <p>I want to display on the user page, the sum of the distance and duration of his runs.</p>
  
  <p>I'm not sure if this sum, i.e., total distance and total duration should be attributes of the user, or if it's should be calculated on the <code>ViewProfileController</code> just in order to display it on his profile.</p>
  
  <p>What would be the correct practice?</p>