Swift + Add Custom Left Bar Button Item on Navigation Bar

 In View Did Load

//---   Add Custom Left Bar Button Item   ---//

        self.addLeftNavItemOnView()

    func addLeftNavItemOnView ()

    {

       // hide default navigation bar button item

        self.navigationItem.leftBarButtonItem = nil;

        self.navigationItem.hidesBackButton = true;

        

        

        let buttonBack: UIButton = UIButton.buttonWithType(UIButtonType.Custom) as UIButton

        buttonBack.frame = CGRectMake(0, 0, 40, 40)

        buttonBack.setImage(UIImage(named:"ImageName.png"), forState: UIControlState.Normal)

        buttonBack.addTarget(self, action: "leftNavButtonClick:", forControlEvents: UIControlEvents.TouchUpInside)

        

        var leftBarButtonItem: UIBarButtonItem = UIBarButtonItem(customView: buttonBack)

        

        self.navigationItem.setLeftBarButtonItem(leftBarButtonItem, animated: false)

        

        

    }

    

    func leftNavButtonClick(sender:UIButton!)

    {

        self.navigationController?.popViewControllerAnimated(true)

    }