使用多个反应数据集写入到 downloadHandler shiny 下的 excel 工作簿

Question

Good afternoon, thank you in advance for taking the time to read my question. In my Shiny app, I am trying to create a list of the reactive objects to write to a single excel workbook for the user to download. I was able to use parts of responses from other posts to replicate my issue and I get pretty close to a resolution. However, while the example below uses a list of dataframes, such as mtcars, iris, etc, I am trying to use reactive datasets, such as datasetInput1(), datasetInput2(), etc.

shinyApp(
    ui = fluidPage(
        downloadButton("downloadExcelSheet", "Download Excel Workbook with Multiple Sheets")
    ),
    server = function(input, output) { 

        #### Write an Excel workbook with one sheet per dataframe ####
        output$downloadExcelSheet <- downloadHandler(
            filename = function() {
                "excelWorkbook.xlsx"
            },
            content = function(file) {
                # write workbook and first sheet
                write.xlsx(mtcars, file, sheetName = "mtcars", append = FALSE)

                # add other sheets for each dataframe
                listOtherFiles <- list(iris = iris, 
                                       airquality = airquality, 
                                       sleep = sleep)
                for(i in 1:length(listOtherFiles)) {
                    write.xlsx(listOtherFiles[i], file, 
                               sheetName = names(listOtherFiles)[i], append = TRUE)
                }
            }
        )

When I try to use these reactive objects in the example below, I am able to successfully download the data when there is just one dataset in the list. For example, the below works, but once I start adding more to the list listOtherFiles such as listOtherFiles <- list(datasetInput2(), datasetInput3()), I get an error.

shinyApp(
    ui = fluidPage(
        downloadButton("downloadExcelSheet", "Download Excel Workbook with Multiple Sheets")
    ),
    server = function(input, output) { 

datasetInput1 <- reactive({

    data %>% 
      filter(sub_date == input$date, app_type == input$type)
})


datasetInput2 <- reactive({

    data2 %>% 
      filter(sub_date == input$date, app_type == input$type)
})

        output$downloadExcelSheet <- downloadHandler(
            filename = function() {
                "datasetOutput.xlsx"
            },
            content = function(file) {
                # write workbook and first sheet
                write.xlsx(datasetInput1(), file, sheetName = "dataset1", append = FALSE)

                # add other sheets for each dataframe
                listOtherFiles <- list(datasetInput2())

                for(i in 1:length(listOtherFiles)) {
                    write.xlsx(listOtherFiles[i], file, 
                               sheetName = names(listOtherFiles)[i], append = TRUE)
                }
            }
        )

Answer 1

datasetInput1() is a reactive value not defined within the server logic. This needs to be assigned a value first or a function created to update values.

The following are some useful articles to understand shiny's reactive elements:

https://shiny.rstudio.com/articles/understanding-reactivity.html

https://shiny.rstudio.com/articles/reactivity-overview.html

Answer 2

I'm not sure I can reproduce the problem. Here is my example below. This seems to work and uses two reactive expressions. Does it work for you?

If not, please edit your question and describe further. Perhaps include example data and ui with inputs to reproduce. What was your error?

library(xlsx)
library(shiny)
library(tidyverse)

shinyApp(
  ui = fluidPage(
    downloadButton("downloadExcelSheet", "Download Excel Workbook with Multiple Sheets")
  ),
  server = function(input, output) { 

    datasetInput1 <- reactive({
      iris %>% 
        filter(Species == "setosa")
    })

    datasetInput2 <- reactive({
      iris %>% 
        filter(Species == "versicolor")
    })

    #### Write an Excel workbook with one sheet per dataframe ####
    output$downloadExcelSheet <- downloadHandler(
      filename = function() {
        "excelWorkbook.xlsx"
      },
      content = function(file) {
        # write workbook and first sheet
        write.xlsx(mtcars, file, sheetName = "mtcars", append = FALSE)

        # add other sheets for each dataframe
        listOtherFiles <- list(setosa = datasetInput1(), versicolor = datasetInput2())
        for(i in 1:length(listOtherFiles)) {
          write.xlsx(listOtherFiles[[i]], file, 
                     sheetName = names(listOtherFiles)[i], append = TRUE)
        }
      }
    )
  }
)