How do i add a cancel on a navigation bar programatically

let btnCancel = UIButton()

btnCancel.setImage(UIImage(named: "crossbuttonimagename"), forState: .Normal)

btnCancel.frame = CGRectMake(0, 0, 25, 25)

btnCancel.addTarget(self, action: Selector("youraction"), forControlEvents: .TouchUpInside)

//Set Left Bar Button item

let leftBarButton = UIBarButtonItem()

leftBarButton.customView = btnCancel

self.navigationItem.leftBarButtonItem = leftBarButton