If you go back to XCode, the files "DataModel.m" and "DataModel.h" should be present under Groups & Files. Where they went to depends on what was selected, if necessary drag them to the Classes tab.
Change the header file so that it looks like this:
With this @property directive, and a corresponding one in the .m file, we don't need to set accessor methods for our variable dataArray, and bindings will also work fine too.
In the implementation file, put in the code from the first post for the loadFakeData method. The top part of the file looks like this:
We don't actually need an init method but it doesn't hurt. And it gives us a convenient place to call our other method, early enough so that when the application window appears it will look like this: