Swift 重构: 导航栏下拉单选菜单解耦

重构实现：

• 通过扩展实现，低解耦；
• Cell 可自定义，适用范围扩展；
• 下拉列表高度可调整；
• 调用简单；

Screenshot:

example:

class NNButtonStudyController: UIViewController{

    var normlImage = UIImage(named: "icon_selected_no_default")!
    var seletedImage = UIImage(named: "icon_selected_yes_green")!
    
    lazy var btn: UIButton = {
        let sender = UIButton(type: .custom)
        sender.setTitle("默认样式", for: .normal);
//        sender.adjustsImageWhenHighlighted = false
        
        if #available(iOS 13.0, *) {
            sender.setImage(UIImage.chevron_down, for: .normal)
            sender.setImage(UIImage.chevron_up, for: .selected)
        }

        sender.sizeToFit()
        sender.layoutButton(direction: 3, imageTitleSpace: 8)
        sender.addTarget(self, action: #selector(handActionBtn(_:)), for: .touchUpInside)

        sender.topMenuTarget.items = [String].init(count: 6, generator: { "icon_selected_no_default_\($0)" })
        sender.topMenuTarget.selectedBlock = {
            let title = sender.topMenuTarget.items[$0]
            sender.setTitle(title, for: .normal)
            sender.sizeToFit()
            sender.layoutButton(direction: 3, imageTitleSpace: 8)
        }
        sender.topMenuTarget.cellForRowBlock = { tableView, indexPath in
            let cell = UITableViewCellOne.dequeueReusableCell(tableView, identifier: UITableViewCellOne.reuseIdentifier, style: .subtitle)
            
            cell.imageView?.image = UIImage.img_update
            cell.textLabel?.text = sender.topMenuTarget.items[indexPath.row]
            cell.detailTextLabel?.text = sender.topMenuTarget.items[indexPath.row]
            return cell
        }
        return sender
    }()
}

    // MARK: -life cycle
    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        navigationItem.titleView = btn
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        
        btn.topMenuTarget.dismiss(false)
    }

    //MARK: -functions
    @objc func handActionBtn(_ sender: NNButton) {
        sender.isSelected.toggle()
        if sender.isSelected {
            sender.topMenuTarget.show()
        } else {
            sender.topMenuTarget.dismiss()
        }
    }
}

Github