@interface AppDelegate : NSObject <NSApplicationDelegate>
{
    NewRepoWindowController* newRepoSheet;
}

- (IBAction)addRepo:(id)sender;

@property (assign) IBOutlet NSWindow *window;

@end

#import "AppDelegate.h"
@implementation AppDelegate

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    newRepoSheet = [[NewRepoWindowController alloc] initWithWindowNibName:@"NewRepoWindowController"];
}

- (IBAction)addRepo:(id)sender {

    [NSApp beginSheet: newRepoSheet.window
       modalForWindow: self.window
        modalDelegate: newRepoSheet
       didEndSelector: @selector(didEndSheet:returnCode:contextInfo:)
          contextInfo: nil];

}
@end