R Shiny store the user input from multiple dynamically generated textAreaInput fields in an object in the server part

Question

New to shiny and struggling with this for more than two days now. I have created an application where the user loads .csv data file and chooses one

Answer 1

I have modified the code of the application as per MrFlick's answer. To leave a paper trail of the complete solution, I am posting it below. The few additional modifications I have made include the printout of the list with the variables for each of the generated textAreaInput fields, so that the list can be viewed in the application itself. I have also added some further modifications of the obj, after it is generated, to obtain the list as desired.

If there are more dynamically generated output sections where check boxes and related text areas, the varconst_ index has to be made unique across the different chunks of code (e.g. varconst1_, varconst2_, varconst3_, etc.).

Here is the code:

library(shiny)

ui <- fluidPage(

  mainPanel(
    fileInput(inputId = "file", label = "Choose File", multiple = TRUE, accept = ".csv"),
    uiOutput(outputId = "varCheckBoxesIndivScores"),

    fluidRow(
      column(width = 3,
             uiOutput(outputId = "selectedScoresCheckBoxes")),

      conditionalPanel(condition = "input.selectedScoresCheckBoxes",
                       column(width = 6,
                              uiOutput(outputId = "variablesConstitutingScale")))),
    br(),

    fluidRow(
      conditionalPanel(condition = "input.selectedScoresCheckBoxes",
                       verbatimTextOutput(outputId = "scalesVarList")))
  )
)

server = function(input, output, session) {

  df <- reactive({
    if(is.null(input$file)) {
      return(NULL)
    } else {
      tbl <- fread(input$file$datapath, stringsAsFactors = TRUE)
      return(tbl)
    }
  })

  output$varCheckBoxesIndivScores <- renderUI({
    if(is.null(df())) {
      return(NULL)
    } else if(!is.null(df())) {
      return(tags$div(align = "left",
                      class = "multicol",
                      checkboxGroupInput(inputId = "varCheckBoxesIndivScores",
                                         label = "Select variables",
                                         choices = colnames(df()))))
    }
  })

  output$selectedScoresCheckBoxes <- renderUI({
    if(is.null(df())) {
      return(NULL)
    } else if(!is.null(df())) {
      return(tags$div(align = "left",
                      checkboxGroupInput(inputId = "selectedScoresCheckBoxes",
                                         label = "",
                                         choices = input$varCheckBoxesIndivScores)))
    }
  })

  output$variablesConstitutingScale <- renderUI({
    if(is.null(df())) {
      return(NULL)
    } else if(!is.null(df()) & length(input$selectedScoresCheckBoxes > 0)) {
      var.list.input.fields <- lapply(input$selectedScoresCheckBoxes, function(i) {
        textAreaInput(inputId = paste0("varconst_",i), label = paste("Variables constituting scale", i), 
                      width = "700px", height = "100px", value = NULL)
      })
      var.list.input.fields
    }
  })

  observeEvent(lapply(paste0("varconst_", input$selectedScoresCheckBoxes), function(x) input[[x]]), {
    obj <- Map(function(x) input[[paste0("varconst_",x)]], input$selectedScoresCheckBoxes)
    obj <- sapply(obj, function(i) {
      if(length(i) > 0) {
        strsplit(x = i, split = " ")
      }
    })
    dput(obj)
    output$scalesVarList <- renderPrint({
      if(is.null(df())) {
        return(NULL)
      } else if(!is.null(df()) && length(input$selectedScoresCheckBoxes) > 0 && length(obj) > 0) {
        print(obj)
      }
    })
  })

}

shinyApp(ui = ui, server = server)