How to call a module inside a module when there is a global variable?

[YonghuiDong]

I want to use a module inside another module, when there is no global variable, it works.

See demo code below:

library(golem)
library(shiny)

#1. Define the inner module
inner_module_ui <- function(id) {
  ns <- NS(id)
  fluidPage(
    h1("Inner Module"),
    selectInput(inputId = ns("colName"),
                label = "Select a column name",
                choices = NULL,
                selected = NULL
                )

  )
}

inner_module_server <- function(id, uploadedData) {
  moduleServer(id, function(input, output, session) {
    observeEvent(uploadedData, {
      updateSelectInput(session = session,
                        inputId = "colName",
                        choices = names(uploadedData),
                        selected = names(uploadedData)[1]
                        )
    })
  })
}


#2. Define the outer module
outer_module_ui <- function(id) {
  ns <- NS(id)
  fluidPage(
    h1("Outer Module"),
    fileInput(ns("file"), "Choose a CSV file", accept = ".csv"),
    tableOutput(ns("contents")),
    inner_module_ui(ns("inner_module"))
  )
}

outer_module_server <- function(id) {
  moduleServer(id, function(input, output, session) {
    data <- reactive({
      req(input$file)
      read.csv(input$file$datapath, header = TRUE)
    })

    output$contents <- renderTable({
      data()
    })
    inner_module_server("inner_module", uploadedData = data())
  })
}

#3. Define the main app
app_server <- function(input, output, session) {
  outer_module_server("outer_module")
}

app_ui <- function() {
  navbarPage(
    title = "demo",
    tabPanel("Outer Module", outer_module_ui("outer_module"))
  )
}

#4. Run app
shinyApp(app_ui, app_server)

When I introduce a global variable, the inner module does not work any longer:

library(golem)
library(shiny)

#1. Define the inner module
inner_module_ui <- function(id) {
  ns <- NS(id)
  fluidPage(
    h1("Inner Module"),
    selectInput(inputId = ns("colName"),
                label = "Select a column name",
                choices = NULL,
                selected = NULL
                )
  )
}

inner_module_server <- function(id, uploadedData, global) {
  moduleServer(id, function(input, output, session) {
    observeEvent(uploadedData, {
      updateSelectInput(session = session,
                        inputId = "colName",
                        choices = names(uploadedData),
                        selected = names(uploadedData)[1]
                        )
    })
})}

#2. Define the outer module
outer_module_ui <- function(id) {
  ns <- NS(id)
  fluidPage(
    h1("Outer Module"),
    fileInput(ns("file"), "Choose a CSV file", accept = ".csv"),
    tableOutput(ns("contents")),
    inner_module_ui(ns("inner_module"))
  )
}

outer_module_server <- function(id, global) {
  moduleServer(id, function(input, output, session) {
    observe({
      req(input$file)
      global$Data <- read.csv(input$file$datapath, header = TRUE)
    })
    output$contents <- renderTable({
      global$Data
    })
    inner_module_server("inner_module", uploadedData = global$Data, global = global)
  })
}

#3. Define the main app
app_server <- function(input, output, session) {
  global <- reactiveValues(
    Data = NULL
  )
  outer_module_server("outer_module", global = global)
}

app_ui <- function() {
  tabPanel("Outer Module", outer_module_ui("outer_module"))
}

#4. Run app
shinyApp(app_ui, app_server)

I don't know where the problem is. Thanks a lot for your help.

Dong

[ilyaZar]

Hey @YonghuiDong

I was able to reproduce your example inside a clean golem-skeleton package, find the repo here:

https://github.com/ilyaZar/TestGolem

I fixed some errors along, mostly passing arguments correctly from module to module. Have a look at the specific git-commits, the comments show what I added in a historic sequence.

It does not match your example exactly, because it's a golem-based R package but maybe this helps finding you the error (whatever your true code-base is; I assume that the above is a simplified reprex).

Let me know if it works for you or post the exact error message that could be useful too.

Remark::
Not directly related to your problem, but still you may have a look at this article https://rtask.thinkr.fr/communication-between-modules-and-its-whims/ which outlines how to structure your global reactive values object if your app grows correctly (I fell into this trap and it took me ages to fix that ... so I am just adding this as a side-information).

[YonghuiDong]

Dear @ilyaZar,

Thanks a lot for your kind help! I really appreciate it.

Best regards,

Yonghui Dong