r - updateSelectinput 抛出 session 未找到错误

Question

我正在使用此代码，但在 updateSelectInput 中不断遇到错误:找不到对象“ session ”。当我尝试通过 fileInput 选项上传任何文件时，会发生这种情况。当我删除 updateSelectInput 语句时，该表打印正常。 (请注意，我提供了重现问题所需的最低限度代码，该代码不包括我希望使用 SelectInput 输入的部分)。

library(shiny); library(shinythemes); library(DT)

ui<- fluidPage(
  sidebarLayout(
    sidebarPanel(
      fileInput(inputId = "default_csv",label="input the file"),
      selectInput(inputId = "facility_id1", label="Choose the facilityID column", choices ="FacilityID"),
      numericInput(inputId = "obs", label="Choose number of obs", value=10)
    ),
    mainPanel(
      dataTableOutput(outputId = "table")
    )
  )
)



server<- function(input, output){

  data_set <- reactive({
    data_set<-read.csv(input$default_csv$datapath, stringsAsFactors = FALSE)
    })
  observe({
    req(input$default_csv)
    dsnames <- names(data_set())

    updateSelectInput(session, "facility_id1", label = "Facility ID", 
                      choices = dsnames, selected = "")

    cat("update done")
  })
  output$table<- renderDataTable(head(data_set(),n=input$obs))
}

shinyApp(ui=ui, server=server)

Warning: Error in updateSelectInput: object 'session' not found
Stack trace (innermost first):
    57: updateSelectInput
    56: observerFunc [C:/Users//Desktop/9.R#29]
     1: runApp
ERROR: [on_request_read] connection reset by peer

Answer 1

服务器函数缺少session参数:

server <- function(input, output, session)