title: Interface Builder and Cocoa: wiring up behind an App Controller class
body: <p>I have been following <a href="http://developer.apple.com/library/ios/#documentation/DeveloperTools/Conceptual/IB_UserGuide/QuickStart/QuickStart.html#//apple_ref/doc/uid/TP40005344-CH22-SW27" rel="nofollow">this</a> tutorial. I'm having conceptual trouble at the point where an App Controller class is written, and then added and hooked up within Interface Builder.</p>
  
  <blockquote>
    <p>Adding the AppController Class 
    The next task is to add an instance of the
    new class to the Interface Builder
    document and connect the class
    outlets.</p>
    
    <p>Create an instance of the
    AppController class. In the Interface
    Builder Library window, click Classes.
    Locate the AppController class. Drag
    this class into the document window to
    create an instance named App
    Controller. Connect the App
    Controller’s qcWindow outlet to the
    design window. Hold down the Control
    key. In the document window, drag from
    the App Controller to the Window
    object. Select the qcWindow outlet
    from the list that appears. Connect
    the App Controller’s qcView outlet to
    the QC view in the design window. Hold
    down the Control key. Drag from the
    App Controller to the QC view in the
    design window. Select the qcView
    outlet from the list that appears.</p>
  </blockquote>
  
  <p>Specifically, I don't understand how this App Controller is being used at run-time. All I did was hook up the window and view outlets within IB, and it magically works as if it was being initialized within the <code>applicationDidFinishLaunching:aNotification</code> method of my app delegate. My point is, I'm not using my App Controller class anywhere in my code, and all I've done in IB is hook up its outlets, so how does it work?</p>