Test file saving on Shiny server

app.R

# Shiny app with 3 fields that the user can submit data for
ui <- fluidPage(
  DT::dataTableOutput("responses", width = 300), tags$hr(),
  textInput("name", "Name", ""),
  checkboxInput("used_shiny", "I've built a Shiny app in R before", FALSE),
  sliderInput("r_num_years", "Number of years using R",
              0, 25, 2, ticks = FALSE),
  actionButton("submit", "Submit")
)

server <- function(input, output) {
  
  # Whenever a field is filled, aggregate all form data
  formData <- reactive({
    data <- sapply(fields, function(x) input[[x]])
    data
  })
  
  # When the Submit button is clicked, save the form data
  observeEvent(input$submit, {
    saveData(formData())
  })
  
  # Show the previous responses
  # (update with current response when Submit is clicked)
  output$responses <- DT::renderDataTable({
    input$submit
    loadData()
  })
  
  outputDir <- "responses"
  
  saveData <- function(data) {
    data <- t(data)
    # Create a unique file name
    fileName <- sprintf("%s_%s.csv", as.integer(Sys.time()), digest::digest(data))
    # Write the file to the local system
    write.csv(
      x = data,
      file = file.path(outputDir, fileName), 
      row.names = FALSE, quote = TRUE
    )
  }
  
  loadData <- function() {
    # Read all the files into a list
    files <- list.files(outputDir, full.names = TRUE)
    data <- lapply(files, read.csv, stringsAsFactors = FALSE) 
    # Concatenate all data together into one data.frame
    data <- do.call(rbind, data)
    data
  }
  
  # Define the fields we want to save from the form
  fields <- c("name", "used_shiny", "r_num_years")
}

shinyApp(ui = ui, server = server)