Using similar UI script in R shiny under multiple subMenuItems

Question

the given R shiny script creates a dropdown menu in the sidebar with main and sub menu items. When you click on the first sub-item 1, you get two selectInputs in the dashboardBody. I want a functionality where I just declare these inputs once and use it multiple times in the other sub-items, just like how reactive function does.I want to do this to make the script fast and efficient. I have less knowledge of reactive functionality, please help and thanks.

library(shiny)
library(shinydashboard)
ui <- dashboardPage(
dashboardHeader(), 
dashboardSidebar(
sidebarMenu(

  id = "tabs",
  menuItem("Charts", icon = icon("bar-chart-o"),
           menuSubItem("Sub-item 1", tabName = "subitem1"),
           menuSubItem("Sub-item 2", tabName = "subitem2"),
           menuSubItem("Sub-item 3", tabName = "subitem3"),
           menuSubItem("Sub-item 4", tabName = "subitem4")
        ))),
  dashboardBody(
  tabItems(
  tabItem("subitem1", column(2,offset = 0, style='padding:1px;', 
  selectInput("select1","select1",c("A1","A2","A3"), selected = "A1")),
          column(2,offset = 0, style='padding:1px;', 
  selectInput("select2","select2",c("A3","A4","A5"), selected = "A3"))),
  tabItem("subitem2", "Widgets tab content"),
  tabItem("subitem3", "Sub-item 1 tab content"),
  tabItem("subitem4", "Sub-item 2 tab content"))))
  server <- function(input, output, session) {
  }
  shinyApp(ui, server)

Answer 1

Your code can be rewritten with shiny modules. The UI module where you want to display the two dropdowns can be written as one (Ui function) and then can be referred in the places you want.

Modified code:

library(shiny)
library(shinydashboard)

submenuUI <- function(id) {
  ns <- NS(id)


  # return a list of tags
  tagList(
     column(2,offset = 0, style='padding:1px;', 
                               selectInput(ns("select1"),"select1",c("A1","A2","A3"), selected = "A1")),
            column(2,offset = 0, style='padding:1px;', 
                   selectInput(ns("select2"),"select2",c("A3","A4","A5"), selected = "A3"))
  )


}


submenu <- function(input,output,session){}


ui <- dashboardPage(
  dashboardHeader(), 
  dashboardSidebar(
    sidebarMenu(

      id = "tabs",
      menuItem("Charts", icon = icon("bar-chart-o"),
               menuSubItem("Sub-item 1", tabName = "subitem1"),
               menuSubItem("Sub-item 2", tabName = "subitem2"),
               menuSubItem("Sub-item 3", tabName = "subitem3"),
               menuSubItem("Sub-item 4", tabName = "subitem4")
      ))),
  dashboardBody(
    tabItems(tabItem("subitem1", submenuUI('submenu1')),
      tabItem("subitem2", submenuUI('submenu2')),
      tabItem("subitem3", submenuUI('submenu3')),
      tabItem("subitem4", "Sub-item 2 tab content"))))
server <- function(input, output, session) {
  callModule(submenu, "submenu")
}
shinyApp(ui, server)