R Shiny:“全球"server.R 中所有函数的变量 [英] R Shiny: "global" variable for all functions in server.R

问题描述

我将 global 放在引号中，因为我不希望 ui.R 可以访问它，而只能在 server.R 中的每个函数中访问它.这就是我的意思:

I put global in quotes because I don't want it to be accessible by ui.R, just accessible throughout every function in server.R. Here's what I mean:

shinyServer(function(input, output, session) {
  df <- NULL
  in_data <- reactive({
    inFile <- input$file1
    if (is.null(inFile)) return(NULL)     
    else df <<- read.csv(inFile$datapath, as.is=TRUE)  
    return(NULL)
   })
  output$frame <- renderTable({
    df
  })
})

shinyUI(pageWithSidebar(
   sidebarPanel(fileInput("file1", "Upload a file:",
                           accept = c('.csv','text/csv','text/comma-separated-values,text/plain'),
                           multiple = F),),
   mainPanel(tableOutput("frame"))
))

我在 ShinyServer 函数的开头定义了 df，并尝试在 in_data() 中使用 <<- 赋值.但是 df 永远不会改变它的 NULL 赋值(所以 output$frame 中的输出仍然是 NULL).有什么方法可以更改 ShinyServer 函数内 df 的整体值?然后我想在 server.R 中的所有函数中使用 df 作为上传的数据框，这样我只需调用一次 input$file .

I have df defined at the beginning of the shinyServer function, and try to change its global value in in_data() with the <<- assignment. But df never changes its NULL assignment (so the output in output$frame is still NULL). Is there any way to change the overall value of df within a function in shinyServer? I want to then use df as the uploaded data frame throughout all of my functions in server.R so that I only have to call input$file once.

我看了this 帖子，但是当我尝试类似的东西时，却抛出了错误，指出没有找到 envir=.GlobalENV.总体目标是只调用一次 input$file 并使用存储数据的变量，而不是重复调用 in_data().

I looked at this post, but when I tried something similar, and error was thrown that envir=.GlobalENV wasn't found. The overall goal is to only call input$file once and use the variable the data is stored in instead of repeatedly calling in_data().

非常感谢任何帮助！

推荐答案

使用反应式的想法是正确的方向；但是你没有做对.我刚刚添加了一行，它正在工作:

The idea to use reactive is the right direction; however you didn't do it quite right. I just added one line and it is working:

shinyServer(function(input, output, session) {
  df <- NULL
  in_data <- reactive({
    inFile <- input$file1
    if (is.null(inFile)) return(NULL)     
    else df <<- read.csv(inFile$datapath, as.is=TRUE)  
    return(NULL)
  })
  output$frame <- renderTable({
    call.me = in_data()   ## YOU JUST ADD THIS LINE. 
    df
 })
})

为什么?因为反应式对象与函数非常相似，只有在您调用它时才会执行.因此，您的代码的标准"方式应该是:

Why? Because a reactive object is very similar to a function, which gets executed only when you call it. Thus the 'standard' way of your code should be:

shinyServer(function(input, output, session) {
  in_data <- reactive({
    inFile <- input$file1
    if (is.null(inFile)) return(NULL)     
    else read.csv(inFile$datapath, as.is=TRUE)  
  })
  output$frame <- renderTable({
    in_data()
  })
})

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