A cohesive visual style is important to any web or mobile app. Developers have been doing this on the web using CSS for many years, and for native Android apps Styles and Themes are the standard. For iOS apps, there is UIAppearance. But while powerful and available since iOS 5, many apps still don't take advantage of its abilities.
I'll explain how to use UIAppearance to style all the components of one type the same way across your app, and how to use subclassing to accomplish a CSS-like functionality I'll be using for this tutorial, but everything can be done in as well. For the full code, and to clone the project created in this tutorial, download the ebook on how to use UIAppearance to create iOS app themes.