It sounds like you're creating a second instance of your AppController class in your window's nib file. You can't do that, each instance of an object in a nib file will be instantiated when a nib is unarchived at runtime. This means if you have an AppController instance in MainMenu.xib and also one your MyWindow.xib file, the AppController object will be alloced and initialized twice.
Normally the way you'd handle this is by using the responder chain. In your Window nib, you assign First Responder as the target of your actions. This means that when the action method is called, the app will ask the currently focused view/control (the one that has first responder status) if it responds to the method by calling the -respondsToSelector: method and passing in the action selector.
If the first responder doesn't respond to the method, the message travels up the responder chain until an object that does respond to the method is found. If no object responds to the method, the NSApplication instance handles it and calls NSBeep().
Just before the method is sent to the NSApplication instance, the application delegate is asked if it responds to the selection. In this case, if your AppController object is set as the application delegate, it will receive the message sent as the action from your object in the window nib.
If this isn't clear enough, it's worth reading the Event Handling guide
You don't have to use the responder chain. You can call a method on the application delegate by calling [[NSApp delegate] yourMethod]. You could also store a reference to the app controller by adding it as an instance variable to your NSWindowController object that loads the nib and setting it at creation time, like so:
- (id)initWithAppController:(id)aController
{
self=[super initWithWindowNibName:@"YourWindowNibName"];
if(self)
{
appController = [aController retain];
}
return self;
}
Your window controller can then call methods of your AppController directly.