This is how I did it
iOS 10 and below
func setUpMenuButton(){
let menuBtn = UIButton(type: .custom)
menuBtn.frame = CGRect(x: 0.0, y: 0.0, width: 20, height: 20)
menuBtn.setImage(UIImage(named:"menuIcon"), for: .normal)
menuBtn.addTarget(self, action: #selector(vc.onMenuButtonPressed(_:)), for: UIControlEvents.touchUpInside)
let menuBarItem = UIBarButtonItem(customView: menuBtn)
self.navigationItem.leftBarButtonItem = menuBarItem
}
iOS 11 – Navigation bar come up with Autolayout so frame setting may not work
func setUpMenuButton(){
let menuBtn = UIButton(type: .custom)
menuBtn.frame = CGRect(x: 0.0, y: 0.0, width: 20, height: 20)
menuBtn.setImage(UIImage(named:"menuIcon"), for: .normal)
menuBtn.addTarget(self, action: #selector(vc.onMenuButtonPressed(_:)), for: UIControlEvents.touchUpInside)
let menuBarItem = UIBarButtonItem(customView: menuBtn)
let currWidth = menuBarItem.customView?.widthAnchor.constraint(equalToConstant: 24)
currWidth?.isActive = true
let currHeight = menuBarItem.customView?.heightAnchor.constraint(equalToConstant: 24)
currHeight?.isActive = true
self.navigationItem.leftBarButtonItem = menuBarItem
}