Shiny reactiveUI hangs with multiple uiOutput calls on same condition variable

Question

I am trying to make a reactive UI with sliders that drop in and out via a dropdown in shiny. I have a server with reactiveUI sliders (server.R):

library(shiny)
shinyServer(function(input, output) {
  output$slider1 <- reactiveUI(function() {
    sliderInput("s1", "slide 1", min = 1,  max = 100, value = 1)  
  })

  output$slider2 <- reactiveUI(function() {
    sliderInput("s2", "slide 2", min = 1,  max = 100, value = 1)   
  }) 
})

I can run the server fine with the following code (ui.R):

library(shiny)
shinyUI(pageWithSidebar(
  headerPanel("Hello Shiny!"),
  sidebarPanel(

    selectInput("dataset", "number of buckets:", 
                choices = c(1,2,3)),

    conditionalPanel(
      condition = "input.dataset==2",
      uiOutput("slider1"),uiOutput("slider2")),

    conditionalPanel(
      condition = "input.dataset==1",
      sliderInput("s1", "slide 1", min = 1,  max = 100, value = 1) 
      )
  ),
  mainPanel(
  )
))

but if I try to make both conditionalPanels call uiOutput, the server freezes:

library(shiny)
shinyUI(pageWithSidebar(
  headerPanel("Hello Shiny!"),
  sidebarPanel(

    selectInput("dataset", "number of buckets:", 
                choices = c(1,2,3)),

    conditionalPanel(
      condition = "input.dataset==2",
      uiOutput("slider1"),uiOutput("slider2")),

    conditionalPanel(
      condition = "input.dataset==1",
      uiOutput("slider1") 
      )
  ),
  mainPanel(
  )
))

I have played around with this, and found that it happens anytime that use the same condition variable and multiple uiOutput calls. Any suggestions? Thanks.

Answer 1

See the comment from @Joe for the answer.

Basically, outputIDs and inputIDs have to be unique; two UI elements with the same IDs on the same page emits and error. This is a limitation of the reactivity in shiny.

The work around from @Jim is to create multiple elements for each output or input used by the client, e.g.

 output$slider2_1 <- ...
 output$slider2_2 <- ...