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:

<UIImage: 0x7ff37bd85750>
GET IT
<UIImage: 0x7ff37bd85750>
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!

Answer 1

//Here is the perfect solution To Set back button with Image and Action in default Navigation Bar

First add UIBarButton in Navigation bar

Then Go to property in File inspector in storyboard and add space to hide back button title text

Set image in Ui Bar button image

/Write on click action method/

To enable swipe to pop (back to previous controller), write two line code in ViewDidLoad method

And you will get perfect Back Button with Swipe to back animation

//Note:- To disable back button previous viewcontroller title , add one space in title text in back button in storyboard file inspector