Why we don't override the methods of UITableViewDataSource in the ContactsDataSourceClass?

Since in the ContactListController it just inherit to UITableViewController, which if you open UITableViewController, you'll find that it conform to UITableViewDataSource protocol, and remember since it (UITableViewDataSource ) have optional protocols, UITableViewController doesn't need to use the all the methods form the protocol, different form Swift's protocol.

But, that conformance to UITableViewDataSource makes UITableViewController pretend already conform to UITableViewDataSource.

And then, in the ContactListController, since we want to implement methods that UITableViewDataSource protocol has to construct the table, we override those methods because we are in a class that :

first, we just inherit from a class -> UITableViewController and nothing else. And that class which we inherit, conform to UITableViewDataSource. It also pretends to already satisfy requirements of the protocol( UITableViewDataSource) but it doesn't use any of its method.

second, the UITableViewController pretend already conform to UITableViewDataSource protocol, it also tell class that subclass it (ContactListController) that it have those method (that it should satisfy) (once again which it doesn't have any of those -_-) . Because of that, if anyone want to use UITableViewDataSource methods, we need to override it, because now those are method now became UITableViewController's.

conclusion: in the UITableViewDataSourceClass we directly conform to UITableViewDataSource (since it is a protocol) so we don't override those methods