Having trouble understanding how UINavigationController and UITabbarController work in Interface Builder

I have just been using Objective-C and Xcode for a little over a month now and I am understanding the code and API pretty well. But there are two things that have been eluding my understanding, Tabbars and Navigation Controllers. If I start a new project I can figure it out (at least the tab bars) but im a little foggy on how to implement this stuff on existing projects. I think I am correct in dragging the controller into IB and then I need to set its delegate and outlet but then it开发者_JAVA百科 doesn't work, after just randomly trying to connect things for an hour or so I can figure out how to get tabbars to work but I don't really understand what I did. UINavigationControllers are even more confusing. I have a book on iOS programming but it pretty much just tells you to start from a template, and reading the Apple Developers Documentation doesn't seem like it really explains what I am doing and what things are kinda the minimal to get it working.

So I guess what I am looking for is a tutorial or write-up that explains how these objects interact with everything and what I actually need to do to integrate it into existing projects, I really need something that is explaining the "theory" behind it, not just steps.

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Both of these questions are explained in the Apple document "View Controller Programming Guide for iOS".

• How to create a Tab Bar controller, step by step
• How to create a Navigation controller interface, step by step