ios - UIViewController 多重继承

Question

我有一个名为 BaseViewController 的类，它包含一个函数，我可以在其中向我的 VC 添加 header 并将其锚定

class BaseViewController: UIViewController {

    let headerView: UIView = {
        let view = UIView()
        view.backgroundColor = UIColor.green
        return view
    }()

    func addHeader() { 
        view.addSubview(headerView)
        // then anchor it to top
    }

}

我有另一个名为 ScrollViewController 的类，它向我的 VC 添加了一个 scrollViewController 并锚定了它

class ScrollViewController: UIViewController {

    let scrollView: UIScrollView = {
        let view = UIScrollView()
        view.backgroundColor = UIColor.green
        return view
    }()

    func addScrollView() { 
        view.addSubview(scrollView)
        // then anchor it to top
    }

}

最后，我的主类 HomeViewController 想要同时拥有一个 header 和一个 scrollView，所以我像这样从两者继承:

class HomeViewController: ScrollViewController, BaseViewController {

    override viewDidLoad() {
        super.viewDidLoad()

        addScrollView()
        addHeaderView()

        let view = UIView()
        //anchor view to bottom of the header
    }
}

但是 swift 不允许多重继承，所以我尝试使用有效的协议(protocol)和扩展，但问题是我希望其他 View 能够锚定到标题和 scrollView，所以它不符合我的需要。

我该怎么做才能实现类似的东西

谢谢

Answer 1

Swift 不支持多重继承。但是，协议(protocol)和协议(protocol)扩展可以完成您想要的。

例子:

protocol HeaderProtocol {
    func addHeaderView() -> UIView
}

extension HeaderProtocol where Self: UIViewController {
    func addHeaderView() -> UIView {
        let headerView = UIView()
        headerView.backgroundColor = UIColor.green
        view.addSubview(headerView)
        // then anchor it to top

        return headerView
    }
}

protocol ScrollViewProtocol {
    func addScrollView() -> UIView
}

extension ScrollViewProtocol where Self: UIViewController {
    func addScrollView() -> UIView {
        let scrollView = UIScrollView()
        scrollView.backgroundColor = UIColor.green
        view.addSubview(scrollView)
        // then anchor it to top

        return scrollView
    }
}

class HomeViewController: UIViewController, ScrollViewProtocol, HeaderProtocol {
    override func viewDidLoad() {
        super.viewDidLoad()

        let scrollView = addScrollView()
        let headerView = addHeaderView()
    }
}

替代方法:

protocol HeaderProtocol {
    var headerView: UIView? { get set }
    func addHeaderView() -> UIView
}

extension HeaderProtocol where Self: UIViewController {
    func addHeaderView() -> UIView {
        let headerView = UIView()
        headerView.backgroundColor = UIColor.green
        view.addSubview(headerView)
        // then anchor it to top

        return headerView
    }
}

protocol ScrollViewProtocol {
    var scrollView: UIView? { get set }
    func addScrollView() -> UIView
}

extension ScrollViewProtocol where Self: UIViewController {
    func addScrollView() -> UIView {
        let scrollView = UIScrollView()
        scrollView.backgroundColor = UIColor.green
        view.addSubview(scrollView)
        // then anchor it to top

        return scrollView
    }
}

class HomeViewController: UIViewController, ScrollViewProtocol, HeaderProtocol {
    var scrollView: UIView?
    var headerView: UIView?

    override func viewDidLoad() {
        super.viewDidLoad()

        scrollView = addScrollView()
        headerView = addHeaderView()
    }
}