Swift - bar button item image / set size and width - swift

Question

Feel like I've been wasting a lot of time on this one and would love some help. I'm trying to use a custom menu icon (20px x 20px) in my barButtonItem. The problem it that is scales to fill the bar button item and is distorted.
Normally this shouldn't be too complicated. But I'm using tabbed view controllers and not a navigation controller. The navigation bar I have dropped into the view controller is just an outlet.
Normally I could do something like this:
let image = UIImage(named: "menu_white")
let frame = CGRectMake(0, 0, image!.size.width, image!.size.height)
let button = UIButton()
button.frame = frame
button.setImage(image, forState: .Normal)
let rightMenuButton = UIBarButtonItem(customView: button)
self.navigationItem.setRightBarButtonItem(rightMenuButton, animated: true)
But this doesn't work because self.navigationItem doesn't actually refer to anything in the view controller.
I need to somehow get the image into the outlet programmatically but setRightBarButtonItem is not a method of UINavigationBar.
#IBOutlet weak var navBar: UINavigationBar!
Would really appreciate some help if anyone's got some ideas.

Answer 1

The way a "loose" navigation bar works is that you configure a UINavigationItem and set an array containing that to be the navigation bar's items, as in this example code (from my book):
let ni = UINavigationItem(title: "Tinker")
let b = UIBarButtonItem(title: "Evers", style: .Plain, target: self, action: "pushNext:")
ni.rightBarButtonItem = b
self.navbar.items = [ni]
So, you could presumably do something like that.
The self.navigationItem thing is merely a way of causing that to be done automatically in the special situation where you're using a UINavigationController. But you say that you're not doing that. (Of course, you could do that; there's no law that says you have to use a navigation controller to do any actual navigation. I often use a navigation controller just to get the navigation bar, because it's a good place to put things like little menu buttons.)