In iOS apps, data is often presented using a table view. Table views are highly optimized for performance; they are easy to use and to implement. We will use a table view for the list of to-do items.

A table view is usually represented by UITableViewController, which is also the data source and delegate for the table view. This often leads to a massive table View Controller because it is doing too much: presenting the view, navigating to other view controllers, and managing the presentation of the data in the table view.

It is a good practice to split up the responsibility into several classes. Therefore, we will use a helper class to act as the data source and delegate for the table view. The communication between the Table View Controller and the helper class will be defined using a protocol. Protocols define what the interface of a class looks like. This has...