Introduction

Next we’ll turn our attention to the theory of reactivity that underlies the magic of Shiny:

Overview of “Mastering reactivity” chapters

• In chapter 13  Why reactivity will you learn why the reactivity programming model is needed, and a little bit about the history of reactive programming outside of R.
• In chapter 14  The reactive graph will you learn the full details of the reactive graph, which determines exactly when reactive components are updated.
• In chapter 15  Reactive building blocks will you learn about the underlying building blocks, particularly observers and timed invalidation.
• In chapter 16  Escaping the graph will you learn how to escape the constraints of the reactive graph using reactiveVal() and observe().

You certainly don’t need to understand all these details for routine development of Shiny apps. But improving your understanding will help you write correct apps from the get-go, and when something behaves unexpectedly you can more quickly narrow in on the underlying issue.