title: How to deal with model classes in iOS application
body: <p>I am a newbie in iOS application development, but I am trying to learn how to deal with Cocoa in the best way.</p>
  
  <p>I got stuck trying to understand how to keep and reference the model objects properly.</p>
  
  <ol>
  <li>many say to write an app delegate property to hold the model and then reference it through the convenience methods for the app delegate singleton.</li>
  <li>others say to "inject" in the view controller only the part of model which it needs (or its subviews needs), but I don't understand how to do this. Via a property? Via an initWithModel: method (and in this case, how can I say to IB to use that method?)</li>
  <li>others again say that the model should be a singleton</li>
  <li>and again, others say to use global variables (!)</li>
  </ol>
  
  <p>Could you please give me some hint (and code samples)? I would like to learn the things in the proper manner, considering that soon I will be moving towards Core Data.</p>