带有空表的闪亮 R renderDataTable

Question

What is the best way to only render a data table in shiny if data exists? Right now, I am getting the following error because I am telling shiny to render a data table, even when it is NULL.

    Warning in file(file, "rt") :
    cannot open file '\': No such file or directory
    Warning: Error in file: cannot open the connection

My code is split like this, where I read the data once the user chooses a csv file. After a user chooses a csv file, the error goes away and everything works fine. How do I tell Shiny to not display a data table until a valid file is chosen?

filedata <- reactive({
  if (is.null(input$file_selector)){
    # User has not uploaded a file yet
    return(NULL)
  } else {
  read.csv(paste0(parseDirPath(c(home = 'C:\\Users\\Ruben'), file_dir()),'\\',input$file_selector),skip=1)}
})

output$filetable <- renderDataTable({
  filedata()
})

I've tried putting the output$filetable <- .... code after the read.csv... line in the filedata <- ... function, but that doesn't work either. What else should I be doing here?

Answer 1

Please use req() , as shown below

filedata <- reactive({
  req(input$file_selector)
  read.csv(paste0(parseDirPath(c(home = 'C:\\Users\\Ruben'), file_dir()),'\\',input$file_selector),skip=1)
})

Answer 2

You can use req() function, this will check whether the file the file is present or not then it will go to the proceding code

filedata <- reactive({
  file <-input$file_selector
  req(file)
  read.csv(paste0(parseDirPath(c(home = 'C:\\Users\\Ruben'), file_dir()),'\\',file),skip=1)}
})