iOS: What is inside an XIB?

I don't like the fact that XIB is an opaque 开发者_JS百科object... Even if I look at the raw XML, I can't really figure out what is going on. I can't find any documentation or guides.

Is there some tool that generates this code? It would be very educational to see the XIB code generated by, say, one of Apple's standard templates, so as to get some idea...

The tool is Interface Builder or was until this was integrated into Xcode 4. See Stack Overflow question What is the internal structure of an Interface Builder .xib file?.

From What are XIB files?:

The crucial difference between XIB and NIB for deployment is that a XIB is not a deployable file. Xcode 3 will compile a XIB into a deployable NIB when the project is built and will include that deployable NIB in the finished application.

I have found one tool, nib2objc. I downloaded the source code and tried to build it myself (he gives build instructions), but I couldn't find the generated binaries...

I have found a downloadable binary, nib2objc 1.3. However, it is a few minor releases behind the GitHub repository.