swift: setting back button image in nav bar

Question

I'm trying to set the back button image in nav bar in my controller, here's my code in viewDidLoad(): ``` var backImg: UIImage? = UIImage(named: "back_btn.png") println(backImg) if var back_img = backImg { println("GET IT") println(back_img) println(UIControlState.Normal) println(UIBarMetrics.Default) self.navigationController.navigationBar.backItem.backBarButtonItem.setBackButtonBackgroundImage(back_img, forState: UIControlState.Normal, barMetrics: UIBarMetrics.Default) } ``` I tried to put them to viewWillLoad, but getting the same error Console with error message: ``` GET IT VSC14UIControlState (has 1 child) (Enum Value) fatal error: unexpectedly found nil while unwrapping an Optional value ``` I don't know which part went wrong. Seems like the back_img is not nil, but I got error saying it's nil Thanks!

Accepted Answer

I have figured out by looking into sample code. 1) Create a bar button item in storyboard. 2) Link that button to controller using IBOutlet 3) Add image to the button

```
 var backImg: UIImage = UIImage(named: "back_btn")
 backBtn.setBackgroundImage(backImg, forState: .Normal, barMetrics: .Default)
```

PS: image should be added to Images.xcassets folder, see sample code, UICatalog , for details.

swift: setting back button image in nav bar

Solution

Problem