An application's User Interface (UI) is essential for providing the user with an easy way of communicating with a device, be it a computer, a mobile phone, or a tablet. On a mobile device, the user interface is not only essential but the only way to interact with the user. Developers have to cope with various limitations and restrictions when developing applications for mobile devices. The processing power of mobile devices does not match that of desktop CPUs, and the screens are smaller, making the process of choosing what sort of information will be displayed each time somewhat more difficult.

In this chapter, we will discuss the key components of an iOS application's UI. We will see how to use and customize these components to create rich application user interfaces and discuss the similarities and differences they have with their desktop equivalents. The following is a list of these components: