R Shiny: How can I return reactive values from a shiny module to the master server function? - r

Question

I have a simple toy example that uses an add/removeBtn module to add and remove UI from "first" module. I need to keep track of the number of times add/remove has been clicked. If I do not use modules, it is easy, but I am trying to do this in the context of nested modules. Code is below, but basically, I cannot seem to get access to the return from the addRmBtnServer() in the main server function. I am sure it is a simple fix, but I have tried many ways around this, but cannot seem to get access to the result from my call to addRmBtnServer(). Thanks!
library(shiny)
firstUI <- function(id) { uiOutput(NS(id, "first")) }
firstServer <- function(input, output, session, a) {
output$first <- renderUI({
selectInput(session$ns("select"), h4("Select"), paste0(isolate(a()),letters[1:4]))
})
}
removeFirstUI <- function(id) {
removeUI(selector = paste0('#', NS(id, "first")))
}
addRmBtnUI <- function(id) {
ns <- NS(id)
tags$div(
actionButton(inputId = ns('insertParamBtn'), label = "Add"),
actionButton(ns('removeParamBtn'), label = "Remove"),
hr(),
tags$div(id = ns('placeholder'))
)
}
addRmBtnServer <- function(input, output, session, moduleToReplicate, ...) {
ns = session$ns
params <- reactiveValues(btn = 0)
observeEvent(input$insertParamBtn, {
params$btn <- params$btn + 1
callModule(moduleToReplicate$server, id = params$btn, ...)
insertUI(
selector = paste0('#', ns('placeholder')),
ui = moduleToReplicate$ui(ns(params$btn))
)
})
observeEvent(input$removeParamBtn, {
moduleToReplicate$remover(ns(params$btn))
params$btn <- params$btn - 1
})
return(params$btn)
}
ui <- fluidPage(
addRmBtnUI("addRm"),
textInput("a", label = "a", value = 1, width = '150px'),
verbatimTextOutput("view", placeholder = TRUE)
)
server <- function(input, output, session) {
pars <- callModule(
addRmBtnServer, id = "addRm",
moduleToReplicate = list(
ui = firstUI,
server = firstServer,
remover = removeFirstUI
),
)
output$view <- renderText({ pars() })
}
shinyApp(ui = ui, server = server)

Answer 1

As said in the comment, you can pass the values as return values in the corresponding server functions. There is a working example below. I left out the firstUI, firstServer and removeFirstUI implementations since they are irrelevant for your problem.
library(shiny)
addRmBtnUI <- function(id) {
ns <- NS(id)
tags$div(
actionButton(inputId = ns('insertParamBtn'), label = "Add"),
actionButton(ns('removeParamBtn'), label = "Remove"),
hr(),
tags$div(id = ns('placeholder'))
)
}
addRmBtnServer <- function(input, output, session, moduleToReplicate, ...) {
ns = session$ns
params <- reactiveValues(btn = 0)
observeEvent(input$insertParamBtn, {
params$btn <- params$btn + 1
callModule(moduleToReplicate$server, id = params$btn, ...)
insertUI(
selector = paste0('#', ns('placeholder')),
ui = moduleToReplicate$ui(ns(params$btn))
)
})
observeEvent(input$removeParamBtn, {
moduleToReplicate$remover(ns(params$btn))
params$btn <- params$btn - 1
})
return(reactive({params$btn}))
}
ui <- fluidPage(
addRmBtnUI("addRm"),
verbatimTextOutput("view", placeholder = TRUE)
)
server <- function(input, output, session) {
a <- reactive({input$a})
pars <- callModule(
addRmBtnServer, id = "addRm",
moduleToReplicate = list(
ui = function(...){},
server = function(...){},
remover = function(...){}
)
)
output$view <- renderText({ pars() })
}
shinyApp(ui = ui, server = server)