Thanks for your question, @ilandbt ! :]
ViewController receives the businesses from its client, which is an instance of YLPClient and is used to get search results from Yelp.
Each BusinessViewModel knows about only one YLPBusiness. The purpose of BusinessViewModel (like all view models) is transforming model information into values that can be displayed on a view. Hence, one BusinessViewModel transforms one YLPBusiness into values that can be displayed. It’s not required (and doesn’t make sense) for BusinessViewModel to know about all YLPBusiness objects, as it only deals with just one.
However, you’re right that technically the ViewController doesn’t need to hold onto businesses! Rather, it could have immediately converted the businesses into businessViewModels after it receives them from Yelp.
This makes sense for this chapter here, but in a later chapter, you’ll add a Filter to only show certain businesses, based on their star rating.
This Filter uses businesses directly, instead of the view models.
Taking another look at the code, however, this too could have used view models instead of the models directly!
I’ll talk with @jstrawn about updating these chapters to have the view controller hold onto the view models only, instead of the models, in the next iteration of this book. :]