It seems I’m not the only one to find this chapter somewhat intimidating. I get parts of it but it hasn’t all come together for me yet. Can anyone offer a commented walk-through the code provided by the authors in this chapter? I don’t want to skip this and move on to next chapter but I might have to! Damn… 
I’ve come back to the code a bit fresher today and understand what is going on with the double declaration of the assets array(s) now. It’s pretty straight forward in hindsight and just requires thinking about. Rereading chapter 18 and the section on accessor methods helped me out a lot.