R Shiny Nested Dynamic Modules Returning Values Example

app.R

library(shiny)


innerInputUI <- function(id){
  ns <- NS(id)
  tagList(textInput(ns('ttt'), "First text"))
}

innerInputServer <- function(input, output, session){
  ns <- session$ns
  return(input$ttt)
}

inputModuleUI <- function(id){
  ns <- NS(id)
  wellPanel(h3("Input Module"),
            uiOutput(ns('text_pan'))
  )
}

inputModule <- function(input, output, session, num){
  ns <- session$ns
  inputs <- reactive(paste0('text', seq(num())))
  output$text_pan <- renderUI({
    purrr::map(inputs(), function(x){innerInputUI(ns(x))})
  })
  
  vals <- reactiveValues()
  observe({purrr::walk(inputs(), function(x){vals[[x]]<-callModule(innerInputServer, x)})})
  return(vals)
}

outputModuleUI <- function(id){
  wellPanel(h3("Output Module"),
            verbatimTextOutput(NS(id, "txt")))
}
outputModule <- function(input, output, session, ImProxy){
  output$txt <- renderPrint({
    paste(purrr::map(names(ImProxy),~ImProxy[[.x]]))
  })
}

ui <- fluidPage(
  textInput('cnum_pan', label='Number of panels', value='1'),
  inputModuleUI('IM'),
  outputModuleUI('OM')
)   
server <- function(input, output, session){
  num_pan <-reactive(as.numeric(input$cnum_pan))
  MyImProxy <- callModule(inputModule, 'IM', num_pan)
  callModule(outputModule, 'OM', MyImProxy)
}

shinyApp(ui, server)

I have hit this wall many times and I always forget how to return values from Nested Dynamic Modules. When the modules are not dynamic there are other ways but this seems to be one that works in most situtations.

The main point is to return values inside a reactValues, and return the reactValues itself. Then access the reactValues in the parent module, or pass it around.

It does not retain the state of the inputs between changes in the number of panels