title: How to pass values between 2 NSWindowController
body: <p>I am stuck trying to pass data from one NSWindowController to other one.
  I have 2 NSWindowController that has already been instanced and their respective NIB been loaded in screen, in fact firstWindowController load first, get some input from user and do some calculation and save them in several variables and IBOutlets. Upon user action (NSButton) in firstWindowController the secondWindowController load the second Nib window.
  Let say:</p>
  
  <p>firstWindowController.h</p>
  
  <pre><code>@class secondWindowController;
  
  @interface firstWindowController : NSWindowController
  {
  secondWindowController *_secondWindowController;
  }
  @property long double onedata; 
  @property (strong) IBOutlet NSTextField *rZab;
  @property (strong) IBOutlet NSTextField *xZab;
  @end
  </code></pre>
  
  <p>In firstWindowController.m is the code that instance _secondWindowController, do synthesize in all @property's variables and objects and load the associated nib screen. In the same way, onedata variables and both IBOulets get some values assigned. Omitted for simplicity.</p>
  
  <p>secondWindowController.h</p>
  
  <pre><code>@interface secondeWindowController: NSWindowController
  long double newdata;
  -(void)getDataFromFirstWC;
  @end
  </code></pre>
  
  <p>secondWindowController.m</p>
  
  <pre><code>#import "firstWindowController.h"
  #import "secondWindowController.h"
  #import "myAppDelegate.h"
  
  @implementation secondWindowController
  -(void)getDataFromFirstWC
  {
  newdata = 0.0;
  newdata = (_firstWindowController.onedata); 
  // Compilation fails here...
  }
  @end
  </code></pre>
  
  <p>This do not compile. The instance of _firstWindowController is not recognized ??.
   Use of undeclared identifier '_firstWindowController'</p>
  
  <p>The instance of _firstWindowController has been created in my application delegate already and it is responsible to load the first window nib.</p>
  
  <p>Any help to get this done?. Other answers to more o less similar questions have not help me.</p>