R Shiny：下载现有文件

Question

Let's say I have an existing zip file ( out.zip ) in my shiny app (ie located on a server). I would like to have the user be able to download this file. This question is very similar to this one . However, that question zips files within the downloadHandler whereas the zip file already exists in my case.

library(shiny)

app <- list(
  ui = fluidPage(
    titlePanel(""),
    sidebarLayout(
      sidebarPanel(
        downloadButton("downloadData", label = "Download")
      ),
      mainPanel(h6("Sample download", align = "center"))
    )
  ),

  server = function(input, output) {  
    output$downloadData <- downloadHandler(
      filename <- function() {
        paste("output", "zip", sep=".")
      },

      content <- function(file) {
        # not sure what to put here???
      },
      contentType = "application/zip"
    )
  }
)

shiny::runApp(app)

Answer 1

After poking around with different file handling functions I discovered that file.copy can be used to download the file.

I change downloadHandler to:

output$downloadData <- downloadHandler(
  filename <- function() {
    paste("output", "zip", sep=".")
  },

  content <- function(file) {
    file.copy("out.zip", file)
  },
  contentType = "application/zip"
)

Answer 2

A few years later, but I think there is a simpler way if you do not need dynamic file generation by placing the file in the www/ folder of the Shiny app:

|
|- app.R
|- www/
       - downloadme.csv

Then when your Shiny app is live the file is available at shiny-url.com/downloadme.csv - or when testing locally 127.0.0.1:1221/downloadme.csv

eg to use within your Shiny ui:

# in ui somewhere
...
  a(href="downloadme.csv", "Download CSV", download=NA, target="_blank")
...