Exporting selected rows in a custom format in Shiny-CodePudding

I am writing a Shiny application that allows the user to input a CSV file and convert it to a specific XML specifications (OPML, the standard for RSS feeds).

My current issue is uniting the ability to select specific rows and export in the custom format. I can export everything together with the standard downloadButton() with a custom function I've written (generate_opml()) that converts into the proper XML format:

  output$downloadOPML <- downloadHandler(
    filename = function() {
      paste('journal-rss-', Sys.Date(), '.opml', sep='')
    },
    content = function(con) {
      opml <- generate_opml(db)
      cat(saveXML(opml), file = con)
    }
  )

However, I want to be able to export only selected rows, which seems easiest DT::datatable(). This can easily be exported as CSV and few other formats:

output$user_table <- renderDataTable({
      datatable(
        db,
        selection = "none",
        filter="top",
        rownames = FALSE,
        extensions = c("Buttons", "Select"),

        options = list(
          select = TRUE,
          dom = 'Blfrtip',
          buttons =
            list('copy', 'print', list(
              extend = 'collection',
              buttons = list(
                list(extend = 'csv', filename = "File", title = NULL,
                     exportOptions = list(modifier = list(selected = TRUE))),
                list(extend = 'excel', filename = "File", title = NULL,
                     exportOptions = list(modifier = list(selected = TRUE)))),
              text = 'Download'
            ))
        ),
        class = "display"
      )

So my question is whether it's possible to export a custom file type with DT::datatable()? Or is there a way to get downloadButton() to only export selected rows?

CodePudding user response：

The indices of the selected rows are in input$ID_rows_selected where ID is the output id of the datatable. So you can do:

  output$downloadOPML <- downloadHandler(
    filename = function() {
      paste('journal-rss-', Sys.Date(), '.opml', sep='')
    },
    content = function(con) {
      dat <- db[input$user_table_rows_selected, ]
      opml <- generate_opml(dat)
      cat(saveXML(opml), file = con)
    }
  )

However I'm not sure this works if you use the Select extension. Maybe with server=FALSE. Please check.