Shiny dynamic number of UI elements example

server.R

library(shiny)
 
MAX <- 200
 
shinyServer(function(input, output) {
 
   # input$nInputs will be changed infrequently
   # but input$dummy will be changed frequently
   nInputs <- reactive(function() {
      # it would be nice to be able add some code here
      # to make sure that 
      # dynamicOutput_1 ... dynamicOutput_{nInputs}
      # are enabled and
      # dynamicOutput_{nInputs+1} ... dynamicOutput_{MAX}
      # are disabled
      input$nInputs
   })
 
   output$dynamicOutputContainer <- reactiveUI(function() {
      res <- div()
      # building the html in this way is not optimal
      # perhaps tagAppendChildren would be a nice function
      # to pass a list of children instead of one child
      for(i in seq_len(nInputs())) {
         res <- tagAppendChild(res, div(id=paste("dynamicOutput_", i, sep=""), class="shiny-html-output"))
      }
      res
   })
   
   # note that this doesn't work with a for loop
   lapply(seq_len(MAX), function(i) {
      output[['impl']]$defineOutput(
         paste("dynamicOutput_", i, sep=""),
         reactive(function() {
            paste("Dynamic input ", i, " will go here but it depends on input dummy=", input$dummy, sep="")
         })
      )
   })
})

ui.R

library(shiny)

MAX <- 200

shinyUI(pageWithSidebar(
   headerPanel("Dynamic number of UI elements example"),
   sidebarPanel(
      numericInput("nInputs", "Number of inputs:", 10, 1, MAX),
      numericInput("dummy", "Dummy Input:", 10)
   ),
   mainPanel(
      htmlOutput("dynamicOutputContainer")
  )
))

This gist no longer works with current version of shiny