eval(parse(text))) in Shiny

[charlot...@gmail.com]

Hi everybody !!

My app needs to have sliderInputs but the number of these sliders are depending on the operator.
To solve the problem I coded :

n= 10

library("shiny")
runApp(list( 
  ui = fluidPage(
    titlePanel("title panel"),
   
    sidebarLayout(
      sidebarPanel("sidebar panel",
                   uiOutput('SAMPLEselection1'),
                   for(p in 2:(n-1)){                    
                     eval(parse(text= paste("uiOutput(","\'","SAMPLEselection",p,"\'","),",sep="")))
                   }
                   uiOutput('SAMPLEselection10')
                   ),
      mainPanel("main panel"))
  )
  ,
  server = function(input, output, session) {
   
    for(i in 1:n){
      eval(parse(text = paste("output$SAMPLEselection",i, "= renderUI({","\n","selectInput(","\"","SampledirSelection",i,"\"",",","\"", "Choose the Sample to analyze","\"", ",c(1,2,3))","\n","})",sep ="")))
      }
    }


))
But it doesn't work.
I don't why ??!! Perhaps it is not possible to have a "for" in the ui ?
Thanks in advance for your answers.

Charlotte

[Yihui Xie]

If you find you need eval(parse(text)) in shiny, you are almost always
on the wrong way. The super power of eval(parse()) is rarely needed,
and should be avoided for security reasons. Here is an example of how
you can achieve your goal more elegantly without security holes:

library(shiny)
runApp(list(
ui = fluidPage(lapply(1:10, function(i) {
uiOutput(paste0('x', i))
})),
server = function(input, output) {
lapply(1:10, function(i) {
output[[paste0('x', i)]] = renderUI(paste('Hi, this is', i))
})
}
))


Regards,
Yihui

[charlot...@gmail.com]

Thank you very much Yihui !
I am developing the code and I will share it with the group ASAP
Again thank you for your advice !
bye