I've tried to build on a Cocoa app which uses storyboard and Swift in Xcode 6. However, when I tried to alter the title of window from within `NSViewController`, the following code doesn't work.

```
self.title = "changed label"

```

When I wrote the above code in `viewDidLoad()` function, the resultant app's title still remains `window`.

Also, the following code causes an error, since View Controller doesn't have such property as `window`.

```
self.window.title = "changed label"

```

So how can I change the title of window programmatically in Cocoa app which is built on storyboard?