Need to explicitly save Interface Builder stuff

[Eric Isaacson]

Mike Sullivan and I have been discussing a mystery we've been
experiencing: working through the book, when it comes to building and
running the program, it will sometimes not work at first. But then
when we close everything down and come back to it, it works.

I've just figured out why. When you start a build, Xcode knows what
you've been modifying within Xcode, and invites you to save the
changes before building. But Interface Builder is a different
program, and if you make modifications within Interface Builder (like
making buttons on the window, or dragging your mouse to link events to
delegate code), Xcode *doesn't* know about those changes, and so
*doesn't* invite you to save them. You have to remember to save the
changes yourself, before doing your build.

Mike also reports that Chapter 5 is dense with tricky and new stuff,
and will likely take longer than it looks, to work through. Don't
wait until Wednesday night or Thursday afternoon to start it.