R shiny trigger downloadHandler on page loading

Question

I'm building an app that operates regularly when nothing is given in a url query, however if a certain string is given there it should download the file immediately. The download works fine, but when it is run at start up it return a 'download.htm' file instead of the .csv. The reproducible example is not querying the url, but triggers in an observe:

library(shiny)
library(shinyjs)

ui <- fluidPage(
  useShinyjs()
  ,downloadButton("downloadData", "Download")
)

server <- function(input, output) {

  data <- mtcars

  observe({
    print("click MacClickFace")
    runjs("document.getElementById('downloadData').click();")
  })  

  output$downloadData <- downloadHandler(
    filename = function() {
      paste("data-", Sys.Date(), ".csv", sep="")
    },
    content = function(file) {
      write.csv(data, file)
    }
  )
}

shinyApp(ui, server)

How can you trigger the download at launch or are there some security things going on here?

Stéphane Laurent · Accepted Answer · 2019-09-25 05:58:52Z

1

Probably the downloadHandler is not ready. You can use a setTimeout(..., 0):

runjs("setTimeout(function(){document.getElementById('downloadData').click();},0);")

answered Sep 25, 2019 at 5:58

Stéphane Laurent

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