Demo: recording downloads in a Shiny app using {pins} for persistent storage

app.R

shiny::shinyApp(
  ui = shiny::fluidPage(
    shiny::h1("Demo: count downloads"),
    shiny::p("Click the download button and the counter will increment."),
    shiny::downloadButton("report", "Generate report"),
    shiny::textOutput("pin_count"),
  ),

  server = function(input, output) {
    board <- pins::board_connect() # auto-auth if board is on same server as app
    pin_name <- "username/pinname" # change to your pin
    pin_content <- pins::pin_reactive_read(board, pin_name)

    output$pin_count <- shiny::renderText({
      n <- max(pin_content()[["count"]])
      paste("Download count:", n)
    })

    output$report <- shiny::downloadHandler(
      # Generate file
      filename = "report.html",
      content = function(file) {
        tempReport <- file.path(tempdir(), "report.Rmd")
        file.copy("report.Rmd", tempReport, overwrite = TRUE)
        rmarkdown::render(
          tempReport,
          output_file = file,
          params = list(df = pin_content()),
          envir = new.env(parent = globalenv())
        )

        # Increment count in pin
        new_row <- data.frame(
          date = as.character(Sys.Date()),
          count = max(pin_content()[["count"]]) + 1
        )
        pin_updated <- rbind(pin_content(), new_row)
        pins::pin_write(board, pin_updated, pin_name)
      }
    )
  }
)

report.Rmd

---
title: "Demo: download count"
output: html_document
params:
  df
---

This is the content of the pinned data.frame prior to this download:

```{r, echo=FALSE}
knitr::kable(params$df)
```