swift 如何监听 扩展属性？

Question

public var dataList: Array<Any> {
        get {
            var list = objc_getAssociatedObject(self, AssociationKeyFromSelector(#function)) as? Array<Any>;
            if list == nil {
                list = [];
                objc_setAssociatedObject(self, AssociationKeyFromSelector(#function), list, .OBJC_ASSOCIATION_RETAIN_NONATOMIC);
            }
            return list!;
        }
        set {
            objc_setAssociatedObject(self, AssociationKeyFromSelector(#function), newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC);
        }
    }