Programming the iPhone User Experience

UIControl Classes

Cocoa Touch provides a robust set of user interface controls that can be used in iPhone and iPod Touch applications. The controls included in UIKit help ensure consistency across applications by establishing and conforming to a set of defined interaction patterns. Leveraging familiar interaction patterns in your applications can increase usability by reducing the burden of learning the intricacies of a new application. For lightweight, task-oriented mobile applications, a shallow learning curve allows users to find value quickly.

User interface elements can be split into two main categories: those that accept user input and those that do not. Elements that respond to user input are called controls. Examples of controls are buttons, sliders, and switches. Non-control elements include activity indicators and status bars.

Standard controls are descendants of UIControl and implement a special mechanism for sending messages in response to user interaction. As with many standardized aspects of Cocoa, this allows developers to rapidly evolve their application, changing the types of controls on the screen or altering the backend code that responds to user interaction.

The UIControl class is the foundation for all of the standard buttons, switches, and sliders. Figure 7-6 shows the UIControl class tree.

Figure 7-6. The UIControl class tree

The Target-Action Mechanism

In Chapter 6 ...