The UIDataSourceModelAssociation protocol defines an interface for providing persistent references to data objects in your app. Your data source objects can adopt this protocol in order to assist a corresponding table or collection view during the state restoration process. Those classes use the methods of this protocol to ensure that the same data objects (and not just the same row indexes) are scrolled into view and selected.

根据上面引子文档的定义，这个协议用来帮助table view或 collection view保持对数据模型中对象的引用，确保在选中行时，相应的对象也被选中。

我不明白这个协议的作用到底体现在哪里，而且我实现了协议中仅有的两个方法，然后运行程序，点击table view的行，发现它们根本没有被调用过。