iPhone Open Application Development

Section Lists

The UITable object was introduced in Chapter 3 as a means of displaying selectable lists of information. When a table gets long enough, finding an item can be like finding a needle in a haystack. The UISectionList class provides a structure similar to a UITable, only expanded to include individual row groupings and a Rolodex-like scroll bar to quickly flip to a section heading. Each grouping can be assigned a section title, such as genres in a book or the first letter of a contact. You'll find section lists in use in the iPhone's own contact and song lists.

The UISectionList class encapsulates a UISectionTable, which comprises the table portion of the list. Like other tables, the section list uses a data binding. A data binding is an interface to a data source, which is queried by the table for the contents and construction of the table. The data source for a section list provides the callback methods needed to build the section list's groupings, section titles, and individual row cells.

As with other table classes covered in this book, the examples provided here create a subclass of the UISectionList object that can act as the section list and its own data source. This architecture is the easiest to illustrate and ideal for creating specialized reusable classes.

Creating a Section List

To create a section list that can also act as its own data source, subclass UISectionList. The following code creates a class named MySectionList containing the methods for both a section ...