The Core iOS Developer’s Cookbook, Fifth Edition

Creating Controls

The process of building a UIControl generally involves four distinct steps. As Recipe 2-5 demonstrates, you begin by subclassing UIControl to create a new custom class. In that class, you lay out the visual look of the control in your initialization. Next, you build methods to track and interpret touches, and you finish by generating events and visual feedback.

Nearly all controls offer value of some kind. For example, switches have isOn, sliders have a floating-point value, and text fields offer text. The kinds of values you provide with a custom control are arbitrary. They can be integers, floats, strings, or even (as in Recipe 2-5) colors.

In Recipe 2-5, the control layout is basically a colored rectangle. More complex controls ...