Create conditional menuitems and menuSubItems in Shiny

Question

I found how to create dynamically a menu at: http://rstudio.github.io/shinydashboard/structure.html#dynamic-content-1 . But, I cannot figure out how to get what I would need.

With the code given in the link above and if statements, I was able to create or not a WHOLE menu relevant to other inputs in my app. But now what I am looking for is flexibility on each items/subitems. For instance, for a default menu like this:

Analyses

1. Analysis 1
2. Analysis 2
3. Analysis 3

I would like to find a way to only show Analysis 1 and 3 if the files needed for analysis 2 are is not present on the server.

So dependant on my app inputs (drop down menus) and other parameters, I would want to be able to change the menu itself. Is that possible?

So far I have tried to find a way to dynamically concatenate menuItems/subMenuItems but no luck.

I have also tried to cheat and generate strings with the right html tags. But this do not seem to work either. Not sure why yet.

Following up the first comments/answers to my question. I am putting below a minimal example of what I have tried. I appreciate this is an ugly way of doing it and it does not work (no menu appearing). It is all based on Pascallv minimal example in the first answer:

library(shiny)
library(shinydashboard)

ui <- dashboardPage(
 dashboardHeader(title = "Dynamic sidebar"),

  dashboardSidebar(
    sidebarMenuOutput("menu")
  ),

  dashboardBody(selectInput(inputId = "SelectFolder", label = "Select my 
  analysis folder", choices = 
                          c(".", "..", "../.."))) 
)



server <- function(input, output) {

  # whenever input$hide_tab changes through user input, output$menu adapts
  observeEvent(input$SelectFolder,{

    content<-list.files(input$SelectFolder)
    menu <- '<ul id="mymenu" class="sidebar-menu">'
    menu <-paste0(menu,menuItem("analysis 1", tabName = "a1", icon = icon("list-ul")))
   if("app.R" %in% content){
      menu <-paste0(menu,menuItem("analysis 2", tabName = "a2", icon = icon("bar-chart")))
    }
    menu <-paste0(menu,"</ul>") # end of the whole menu
    output$menu <- renderMenu(menu)
  } )  
}


shinyApp(ui, server)

The reason why Pascallv solution does not work for me is because I have a lot of different cases (the menu can be big) and I cannot cover all possible combinations of analyses being present in my folders or not by creating 50+ different menus. Does it make more sense now please?

Answer 1

You could for example use observeEvent() in the server code and by that make the menu react to any change in input you like.

I do not know what exactly you want to do, because you did not provide a minimal example of what you did so far. Yet I am sure you can transfer this example to your code:

library(shiny)
library(shinydashboard)

ui <- dashboardPage(
   dashboardHeader(title = "Dynamic sidebar"),

   dashboardSidebar(
     sidebarMenuOutput("menu")
   ),

  dashboardBody(selectInput(inputId = "hide_tab", label = "Hide a tab?", choices = 
                c("1", "2", "3"))) 
)



server <- function(input, output) {

    # whenever input$hide_tab changes through user input, output$menu adapts
    observeEvent(input$hide_tab,{

    if(input$hide_tab== "1"){
      output$menu <- renderMenu({
      sidebarMenu(
      menuItem("Menu item", menuSubItem("analysis 2"), menuSubItem("analysis 3")))}) 
    }

    if(input$hide_tab== "2"){
        output$menu <- renderMenu({
        sidebarMenu(
        menuItem("Menu item", menuSubItem("analysis 1"), menuSubItem("analysis 
3")))})
    }

    if(input$hide_tab== "3"){
        output$menu <- renderMenu({
        sidebarMenu(
        menuItem("Menu item", menuSubItem("analysis 1"), menuSubItem("analysis 
2")))})
    }

  })
}


shinyApp(ui, server)