Cocoa Multiple Window Controllers - objective-c

Question

I have a Cocoa app that uses automatic reference counting and does not use core-data (not document-based) and I want to be able to create multiple instances of a window I have defined in a nib file.
I currently have this in my AppDelegate:
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
// Insert code here to initialize your application
// for slight performance bump, we assume that users usually have 1 session open.
sessionWindowControllers = [[NSMutableArray alloc] initWithCapacity:1];
}
- (void) awakeFromNib {
// on start, we create a new window
[self newSessionWindow:nil];
}
- (IBAction)newSessionWindow:(id)sender {
SessionWindowController *session = [[SessionWindowController alloc] initWithWindowNibName:#"SessionWindow"];
//add it to the array of controllers
[sessionWindowControllers addObject:session];
[session showWindow:self];
}
SessionWindowController is a subclass of NSWindowController.
but when I run it, I get the runtime error
LayoutManagement[30415] : kCGErrorIllegalArgument:
_CGSFindSharedWindow: WID 11845 Jun 8 18:18:05 system-process LayoutManagement[30415] : kCGErrorFailure: Set a breakpoint #
CGErrorBreakpoint() to catch errors as they are logged. Jun 8
18:18:05 system-process LayoutManagement[30415] :
kCGErrorIllegalArgument: CGSOrderFrontConditionally: Invalid window
Is using NSMutableArray even a good way to manage multiple windows, or is there a better design pattern? Thanks!

Answer 1

Ans. kindly provided by Ben Flynn:
I put the
sessionWindowControllers = [[NSMutableArray alloc] initWithCapacity:1];
in applicationDidFinishLaunching, but since awakeFromNib is called first, we are trying to add an instance of session to the array before it even exists.
Solution: put array init inside the awakeFromNib before we make our first window.
- (void) awakeFromNib {
sessionWindowControllers = [[NSMutableArray alloc] initWithCapacity:1];
[self newSessionWindow:nil];
}