Getting an input list containing inputs present in the current session

Question

I want to retrieve the list of inputs in the current shiny session. We can retrieve the list of inputs using names(input).

I have a uiOutput and based on different conditions I am rendering different types inputs. The current problem I am facing is that when the condition changes the inputs from previous renderUI is also present in the list. Is there a way to get only the inputs in the current session?

To explain my query better I have the following sample code:

   library(shiny)

    ui <- fluidPage(

      sliderInput(inputId = "slider",label = "", min = 1, max = 3, value = 1),

      uiOutput("UI"),

      actionButton(inputId = "btn", label = "Show Inputs"),

      verbatimTextOutput(outputId = "textOp")
    )


    server <- function(input, output){

      observeEvent(input$slider,{

        if(input$slider == 1){

          output$UI <- renderUI(
            textInput("txt1",label = "Slider in position 1")
                      )

        }else if(input$slider == 2){

          output$UI <- renderUI(
          textInput("txt2",label = "Slider in position 2")
          )

        }else{

          output$UI <- renderUI(
          textInput("txt3",label = "Slider in position 3")
                    )
        } 


      })


      observeEvent(input$btn,{

        output$textOp <- renderText(

          paste0(names(input), ",") 
        ) 


       })
    }



    shinyApp(ui = ui, server = server)

In the above code when I first click on action button labelled "Show Input" I get the following text as the output:

btn, slider, txt1,

Now when I move the slider to 2 my output is as follows:

btn, slider, txt1, txt2,

Here txt1 was generated when the slider was at position 1, and this renderUI was overridden by output$UI <- renderUI(textInput("txt2",label = "Slider in position 2")). I want an input list where txt1 is not there. Is there a way to do that?

Possible duplicate http://stackoverflow.com/questions/41031584/collect-all-user-inputs-throughout-the-shiny-app — Pork Chop, May 11 '17 at 11:37
@PorkChop that question refers to saving all the input values, here I want the list element id of the inputs present in current session. I don't want the ids of the input elements that was rendered by renderUI for the previous condition. — SBista, May 11 '17 at 11:47

score 1 · Accepted Answer · answered May 12 '17 at 05:37

I came up with kind of a workaround, assuming you dont have any inputs that should take a value of NULL. You could set the values of the inputs, that you wish to remove, to NULL and filter for non - NULLs when you display the names.

library(shiny)

ui <- fluidPage(
  tags$script("
    Shiny.addCustomMessageHandler('resetValue', function(variableName) {
              Shiny.onInputChange(variableName, null);
              });
              "
  ),
  sliderInput(inputId = "slider",label = "", min = 1, max = 3, value = 1),

  uiOutput("UI"),

  actionButton(inputId = "btn", label = "Show Inputs"),

  verbatimTextOutput(outputId = "textOp")

)


server <- function(input, output, session){

  observeEvent(input$slider,{
    for(nr in 1:3){
      if(nr != input$slider) session$sendCustomMessage(type = "resetValue", message = paste0("txt", nr))      
    }
  })

  output$UI <- renderUI(
    textInput(paste0("txt", input$slider), label = paste0("Slider in position ", input$slider))
  )

  global <- reactiveValues()

  observe({
      inp = c()
      for(name in names(input)){
        if(!is.null(input[[name]])){
          inp <- c(inp, name)
        }
      }
      isolate(global$inputs <- inp)
  })

  output$textOp <- renderText({
    global$inputs
  })
}
shinyApp(ui = ui, server = server)

Thank you. It does answer the question for the given sample code but actually my actual code contains numerous dynamically generated inputs based on different conditions, so resetting value of each input would be quite tedious. Can you suggest any other way to do it? — SBista, May 12 '17 at 05:49
As you might have seen in your research there are quite some discussions concerning similar requests, which didnt yield any other solution. I dont see an easier way, but maybe smdy else comes up with sthg else,... — Tonio Liebrand, May 13 '17 at 15:13

Getting an input list containing inputs present in the current session

1 Answers1