7.8. Pickers

Pickers are click wheels for the iPhone: large, spinning dials that can host any number of different options. Pickers are used in place of drop-down menus to provide a graphically rich selection interface for the user. Close cousin to a control, the UIPickerView class was designed as a full-blown view class due to its sheer size on the screen. This allows it to be used almost anywhere, including a main view or in conjunction with a preferences table.

7.8.1. Creating a Picker

The UIPickerView class contains a UIPickerTable object, which is derived from the UITable object. Like other tables, the UIPickerTable uses a data binding. Unlike other table classes, the picker’s data source isn’t specified with the dataSource method. Instead, a delegate is used for receiving data binding requests in addition to picker events. This was likely done to give the UIPickerView class the simplicity of a control. The UIPickerView data binding is small enough that it can be tucked nicely into controlling views, although the picker itself can also be subclassed to create a self-contained picker.