R Shiny：下载多个.csv文件

Question

I have an issue regarding Shiny on R. I have a function which returns a list with 2 objects as output, both as a matrix. The first one is always created and is always available for download. The second one, is combined with a condition displayed as a checkbox.

global

physical_check <- function(file_path, x,y,z, classification)
input: String, int, int, int, boolean
output: list(matrix1 = result, matrix2 = rating)

UI:

ui <- fluidPage(   
   # Application title
   titlePanel("Review"),

   # Sidebar with a slider input for number of bins 
   sidebarLayout(
     sidebarPanel(
       fileInput('file1', 'Choose .txt File',
                 accept=c('text/csv','text/comma-separated,text/plain')),
       hr(),

       checkboxInput("classification", "Use Text-Classification", value = FALSE),
       hr(),

       downloadButton("download_physic", "Physical Review"),
       br(),
       conditionalPanel(condition = "input.classification == true", 
                        downloadButton("download_classify", "Text Classification"))

     ),
     mainPanel(
       h3("Review"),
       tableOutput("rating"),
       tableOutput("result_shiny")
     )
   )

)

Server:

server <- function(input, output) {
  inFile <- reactive({
    input$file1
  })
  result <- reactive({NULL})

    classify <-  reactive({
    input$classification
  })

  observe({
    if (!is.null(inFile())) {
      result <- reactive({
        withProgress({
          setProgress(message = "Processing review...")
          physical_check(as.String(inFile()$datapath),15,8,3,classify())
        })
      })
    }  

  output$result_shiny <- renderTable({
    result()$result
  })
    output$rating <- renderTable({
    result()$rating
  })

  output$download_physic <- downloadHandler(
    filename = function() {
      sub(pattern = "\\.txt",replacement = "_result.csv",inFile()$name)
    },
    content = function(file) {
      write.table(
        result()$result,
        file,
        sep = ";",
        col.names = NA,
        qmethod = "double"
      )
    }
  )

  output$download_classify <- downloadHandler(
    filename = function() {
      paste("rating", ".csv")
    },
    content = function(file) {
      write.table(
        result()$rating,
        file,
        sep = ";",
        col.names = NA,
        qmethod = double
      )
    }
  )
  }) 
}
# Run the application 
shinyApp(ui = ui, server = server)

So as you can see in the code I mentioned a conditional download button for the text classification, if the checkbox is triggered. According to this TRUE/FALSE value the function physical_check is called with true or false and returns a matrix and NULL or 2 matrizes and only in the second option, the download button is displayed. I'm a little bit confused, because with tableOutput I receive the correct tables in the main panel, also downloading the physical review with the first downloading part works fine. But the second one fails in google chrome with a download error:

download_classify
Failed - Server problem

Although it's constructed the same way.

Answer 1

You forgot to put quotes "" in the qmethod argument. Your download handler for classify should be this:

output$download_classify <- downloadHandler(
      filename = function() {
        paste0("rating", ".csv")
      },
      content = function(file) {
        write.table(
          result()$rating,
          file,
          sep = ";",
          col.names = NA,
          qmethod = "double"
        )
      }
    )