It’s pretty much unavoidable that we’re going to need to pass data around our app at some point. Why? Because apps are made up of a whole bunch of views and user interactions and…stuff, none of which tend to exist in isolation. Whether we’re talking about data pulled in via a REST API, collected from a user input, generated client-side, or whatever else, it is often the case that we’ll need to use it in more than one place to create the types of rich experiences users have come to expect from mobile. At the same time, resources like data usage and battery life are limited on mobile, so we want to keep things like network requests and computation to a minimum whenever possible. Keep it DRY (don’t repeat yourself), as the old saying goes.