title: Push to a UIViewController from inside of NSObject's subclass
body: <p>I am a newbie in Objective-C. I stucked into a very big problem.</p>
  
  <p>I have a ModelClass (named MyModel) for data management which is a subclass of NSObject...
  And to access the data the app needs authentication using a viewcontroller (say X) I don't have access to its properties (Actually it is a framework's viewcontroller)...
  I am accessing that model class from a viewController (named MyViewController)..and I want the retrieval along with authentication of data by calling one method of that model class...but, to present the uncontrolable viewcontroller X for authentication; I must use pushToViewController: method of UINavigationController SDK class.
  And I found that subclasses of NSObject class do not respond to navigationController.</p>
  
  <p>But I really need to do this. Any kind of effective help is appreciated and thanks in advance.</p>