Passing data within Shiny Modules from Module 1 to Module 2

Question

I dont have a reproducible example as the question is more on how modules work. I am trying to understand how to pass some reactive function from one module to the next. I h

Answer 1

One possibility is passing the output from one module to the other at construction time. This allows hierachic relationships between modules. There is also the possibility to create memory that is shared between two modules which I will not cover in this answer.

reactiveValues

Here i created an inputModule and an outputModule. The inputModule recieves two textinputs by the user and the output module displays them via verbatimTextOutput. The inputModule passes the user submitted data to the output module as a reactiveValues object called ImProxy (input module proxy). The outputModule accesses the data just like a list (ImProxy$text1, ImProxy$text2).

library(shiny)

inputModuleUI <- function(id){
  ns <- NS(id)
  wellPanel(h3("Input Module"),
            textInput(ns('text1'), "First text"),
            textInput(ns('text2'), "Second text"))
}
inputModule <- function(input, output, session){
  vals <- reactiveValues()
  observe({vals$text1 <- input$text1})
  observe({vals$text2 <- input$text2})
  return(vals)
}

outputModuleUI <- function(id){
  wellPanel(h3("Output Module"),
            verbatimTextOutput(NS(id, "txt")))
}
outputModule <- function(input, output, session, ImProxy){
  output$txt <- renderPrint({
    paste(ImProxy$text1, "&", ImProxy$text2)
  })
}

ui <- fluidPage(
  inputModuleUI('IM'),
  outputModuleUI('OM')
)   
server <- function(input, output, session){
  MyImProxy <- callModule(inputModule, 'IM')
  callModule(outputModule, 'OM', MyImProxy)
}

shinyApp(ui, server)

This approach can be used with observe or observeEvent as well.

list(reactive)

If you want to use reactive rather than reactiveValues, the following adaptiation of the above code can be used. You can leave the ui functions as they are.

inputModule <- function(input, output, session){
  list(
    text1 = reactive({input$text1}),
    text2 = reactive({input$text2})
  )
}

outputModule <- function(input, output, session, ImProxy){
  output$txt <- renderPrint({
    paste(ImProxy$text1(), "&", ImProxy$text2())
  })
}

shinyApp(ui, server)

reactive(list)

Again, this will give the same functionality for the app but the proxy pattern is slightly different.

inputModule <- function(input, output, session){
  reactive(
    list(
      text1 = input$text1,
      text2 = input$text2
    )
  )
}

outputModule <- function(input, output, session, ImProxy){
  output$txt <- renderPrint({
    paste(ImProxy()$text1, "&", ImProxy()$text2)
  })
}

shinyApp(ui, server)