I am very new to Shiny and I have gone through all the tutorials on the Rstudio website, and have run and tested example apps myself.
I noticed that in Joe Cheng's reactivity videos he always puts session as an argument in the server function like this:
server <- function(input, output, session) {}
while in most of the other examples I see
server <- function(input, output) {}
I know that the session argument is optional, but I wonder whether there is a situation where it is absolutely needed. What is the difference with or without the session argument?
I could not find an explanation anywhere else.