title: How does the cocoa "view" system work?
body: <p>I mean, seriously, I don't get it at all.</p>
  
  <p>I'm writing this app and I need to have a sidebar which changes the content of the main part of the window.</p>
  
  <p>I read several documentations about the ViewController, WindowController, etc.. What I don't understand is how this is all supposed to be "simple" or even modular.</p>
  
  <p>So, let's take this example. </p>
  
  <p>I have this app which consists of a simple menu on the left side, and a main view in the middle which may or may not contain a sub menu (based on which page we are viewing). I would like these views to be on the same window, and to be independent from each other. The main screen should only display its content, and not know anything about the menu, the window, etc..</p>
  
  <p>I created several ViewControllers, one for each view I want to show to the user, each one of them has its Xib file where I can draw the interface I want it to display.</p>
  
  <p>How do I change the main view based on what the user selects on the left size? I'm not talking about the code per se, but rather about how the logic behind it is supposed to work.</p>
  
  <p>Should the window controller know abou its pieces? Should the main menu contain the main window so it can change it? Should I use placeholders (Custom Views) in the main window to insert the other views in?</p>