protocol UIScrollViewDelegate: NSObjectProtocol { ... }
class UIScrollView: UIView {
    ...
    weak var delegate: UIScrollViewDelegate?
    ...
}

然后UITableView与委托变体？

protocol UITableViewDelegate: NSObjectProtocol,UIScrollViewDelegate { ... }
class UITableView: UIScrollView {
    ...
    weak var delegate: UITableViewDelegate?
    ...
}

Apple如何做到这一点？当我做我的

protocol MyScrollViewSubclassDelegate: NSObjectProtocol,UIScrollViewDelegate { ... }
class MyScrollViewSubclass: UIScrollView {
    ...
    weak var delegate: MyScrollViewSubclassDelegate?
    ...
}

我使用’MyScrollViewSubclassDelegate’类型获得Property’委托’不能覆盖类型为“UIScrollViewDelegate？”的属性.