Simple displaying of second window: OS X & Swift

Create: SecondNSWindowController vs SecondNSWindowController.xib

After that, put these codes in your classes and that should do it.

class SecondWindowController: NSWindowController {

convenience init() {
self.init(windowNibName: "SecondWindowController")
}
}

class ViewController: NSViewController {

private var secondWindowController: SecondWindowController?

@IBAction func showSecondWindow(sender: AnyObject) {
if secondWindowController == nil {
secondWindowController = SecondWindowController()
}
secondWindowController?.showWindow(self)
}
}