The Core iOS Developer’s Cookbook, Fifth Edition

Recipe: Building a Star Slider

Rating sliders allow users to grade items such as movies, software, and so forth by dragging their fingers across a set of images. It’s a common task for touch-based interfaces but one that’s not well served by a simple UISlider instance, with its floating-point values. Instead, a picker like the one built in Recipe 2-6 limits a user’s choice to a discrete set of elements, producing a bounded integer value between zero and the maximum number of items shown. As a user’s finger touches each star, the control’s value updates, and a corresponding event is spawned, allowing your application to treat the star slider like any other UIControl subclass.

The art is arbitrary. The example shown in Figure 2-6 uses stars, but ...