justinnichols.com

One of the most difficult things I had to learn when developing an iPhone application with Objective-C is the basics around Navigation. I understood the concept of pushing a view onto the stack, but given the old-natured, procedural code required for UINavigationController, it just wasn’t as simple if you’re on one “page” and you want to navigate to another “page” that you’ve already been to.

The idea is that you want to keep these pages in memory and provide a simple mapped method to get to each one. This is where three20 comes in. three20 is a “framework” (currently just source code, not bundled as a .framework) that gives some much needed guidance concerning UI navigation and UI standard elements/event handling. three20 is the framework behind the very popular Facebook application on the iPhone.

I would go into detail on exactly how helpful this framework is for navigation, but the author of three20 does a considerable better job than I ever could: http://three20.info/ui/navigation.