R上传错误文件时闪烁警告消息 [英] R Shiny warning message when wrong file is uploaded

问题描述

我想在我的闪亮的应用程序的一个功能，当有人上传的文件不是.CSV格式，他们收到一个警告，当他们做的上传.CSV格式，它打印表。这里是我的UI代码

I want to have a feature in my shiny app that when someone uploads a file which is not in .csv format they recieve a warning and when they do upload in .csv format it prints the table. here is my UI code

shinyUI(
tabPanel("File Upload",
                      h4("File Upload"),
                      sidebarLayout(
                        sidebarPanel(
                          fileInput('file1', 'Choose CSV file to upload',
                                    accept = c(
                                      'text/csv',
                                      'text/comma-separated-values',
                                      'text/tab-separated-values',
                                      'text/plain',
                                      '.csv',
                                      '.tsv'
                                    )
                          )
                        ),
                        mainPanel(
                          tableOutput('upload'),
                          h1(textOutput("warning1"))
                          )


                      )

               )
)

和我的服务器代码

shinyServer(function(input, output) {

output$upload <- renderTable({


  #assign uploaded file to a variable
  File <- input$file1

  #catches null exception
  if (is.null(File))
    return(NULL)

  read.csv(File$datapath)

})

output$warning1 <- renderPrint({

  upload<- input$file1
  if (is.null(upload))
    return(NULL)

  if (upload$type != c(
                          'text/csv',
                          'text/comma-separated-values',
                          'text/tab-separated-values',
                          'text/plain',
                          '.csv',
                          '.tsv'
                        )    
      )
  return ("Wrong File Format try again!")


})


}

推荐答案

你真正需要的是 validate 语句。另外，你需要使用％in％函数来检查一个值是否在向量中，只是FYI。以下是一个更简单的实现您的警告/错误。它使用 tools 包中的 file_ext 函数。

All you really need is a validate statement. Also, you would need to use the %in% function to check if a value is in a vector, just FYI. The following is a much simpler implementation for your warning/error. It utilizes the file_ext function from the tools package.

library(shiny)
library(tools)

runApp(
  list(
    ui = tabPanel("File Upload",
               h4("File Upload"),
               sidebarLayout(
                 sidebarPanel(
                   fileInput('file1', 'Choose CSV file to upload',
                             accept = c(
                               'text/csv',
                               'text/comma-separated-values',
                               'text/tab-separated-values',
                               'text/plain',
                               'csv',
                               'tsv'
                             )
                   )
                 ),
                 mainPanel(
                   tableOutput('upload')
                 )
               )

      ),
    server = function(input, output){
      output$upload <- renderTable({

        #assign uploaded file to a variable
        File <- input$file1        

        #catches null exception
        if (is.null(File))
          return(NULL)

        validate(
          need(file_ext(File$name) %in% c(
            'text/csv',
            'text/comma-separated-values',
            'text/tab-separated-values',
            'text/plain',
            'csv',
            'tsv'
          ), "Wrong File Format try again!"))

        read.csv(File$datapath)
      })
    }
    ))

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