Update Shiny's 'selectInput' dropdown with new values after uploading new data using fileInput

Question

I have a Shiny app that includes a number of dropdown selection boxes, the values of which are filled from reading an RDS file. The app also includes a fileInput function to

Answer 1

to riff off of @PoGibas' answer, I needed to load multiple list values for an app, here is a similar application using reactiveValues and observeEvent :

library(shiny)

# save a dummy RDS for loading
saveRDS(list(names=LETTERS,numbers=seq(10)),'dummy.rds')
# define initial values
myDataList <- list(names=c("Tom","Dick","Harry"), numbers=seq(5))

ui <- shinyUI(
  fluidPage(
    fileInput("file1", "Choose file to upload", accept = ".rds"),
    selectInput("myNames","Names", ""),
    selectInput("myNumbers","Numbers", ""),
    tableOutput("contents")
  )
)

server <- function(input, output, session) {

  md <- reactiveValues(
    names = myDataList$names,
    numbers = myDataList$numbers
  )

  observeEvent(input$file1,{
      d <- readRDS(input$file1$datapath)
      for (n in names(d)){
        md[[n]] <- d[[n]]
      }
  })

  output$contents <- renderTable({
   data.frame(data = c(md$names,md$numbers))
  })

  observe({
    updateSelectInput(session, "myNames",
                      label = "myNames",
                      choices = md$names,
                      selected = md$names[1])
    updateSelectInput(session, "myNumbers",
                      label = "myNumbers",
                      choices = md$numbers,
                      selected = md$numbers[1])
  })
}

shinyApp(ui, server)