How to access session$user in Shiny using Shiny Pro - r

Question

I have a simple shiny app that I am testing SHINY pro and I would like to access the session$user like the documentation suggests:
http://rstudio.github.io/shiny-server/latest/#flat-file-authentication. See section 4.1 which shows this code:
shinyServer(function(input, output, session) {
output$username <- reactive({
session$user
})
That code works but I need to access session$user in the ui.r file via the GetUser() function
Here is my ui.r File:
library(shiny)
shinyUI(fluidPage(
textOutput("HeaderTime"),
sidebarPanel(
selectInput("t", "t:", as.character(GetUser()), selected = as.character(GetUser())), width = 2
),
mainPanel(
tabsetPanel(
tabPanel("test",
dataTableOutput("Table"),
plotOutput("Plot"),
# verbatimTextOutput("Txt"),
width = 12
)
)
)
))
You can see the GetUser() function in the selectInput. I have placed GetUser() in my server.R file here:
shinyServer(function(input, output, session) {
GetUser<-reactive({
return(session$user)
})
output$Plot<-renderPlot({
hist(rnorm(1000))
})
output$Table<- renderDataTable({
data.frame(a=c(1,2,3,4),b = c("TEst","test","test","test"))
})
})
when I run this code I get the error:
Error in GetUser() : argument "session" is missing, with no default
Any idea how to allow the ui.r to access GetUser() in the server.r file so session$user can be used in the ui?
Here is code to run project:
library(rJava)
library(shiny)
install.packages("shiny")
runApp("C://me/pathtoproject")
Thank you.

Answer 1

The error you get does address the problem (albeit in a cryptic way).
When you call your GetUser function in the ui, the "session" argument is not known (i.e. it is only "known" by the server).
I suggest to use updateSelectInput (or renderUI if you prefer) and send the session$user value from the server side.
Something like (not tested):
server = function(session,input, output) {
GetUser<-reactive({
return(session$user)
})
updateSelectInput(session, "t", "t:", as.character(GetUser()),selected = as.character(GetUser()))