RShiny 中的响应式(Reactive)输入 react 太快(不使用按钮)

Question

如何才能让 Shiny 等待用户输入邮政编码(不使用按钮)。我面临的问题是，如果用户输入邮政编码的速度不够快，它会很快跳转到错误。 编辑:

• 我在这个应用程序中有其他用户输入，但我在这个问题中简化了它。我希望所有其他输入立即使用react，因为它们是单选按钮。我认为按“返回”仍然会执行与按钮相同的操作，这不是我想要的。我正在考虑仅将“Sys.sleep()”用于邮政编码输入，而不用于其他输入。这可能吗？

library(shiny)

shinyApp(ui <- fluidPage(sidebarPanel(
  "",
  textInput("zipcode", label = "Enter your zipcode.", value = 98125)
  
)) ,


server <- function(input, output, session) {
  observeEvent(input$zipcode, {
    #limits zipcode input to 5 numbers only
    if (nchar(input$zipcode) != 5)
    {
      updateTextInput(session, 'zipcode', value = 98125)
      showModal(
        modalDialog(
          title = "Error!",
          "Only 5-character entries are permitted.",
          easyClose = TRUE
        )
      )
    }
    if (is.na(as.numeric(input$zipcode)))
    {
      showModal(
        modalDialog(
          title = "Error!",
          "Only numeric values are allowed. Please try again.",
          easyClose = TRUE
        )
      )
    }
  })
})

Answer 1

您可以使用debounce :

This lets you ignore a very "chatty" reactive expression until it becomes idle, which is useful when the intermediate values don't matter as much as the final value

您不需要 Sys.sleep，它会在触发 react 之前等待 millis 毫秒:

library(shiny)

shinyApp(
  ui <- fluidPage( 
    sidebarPanel("", textInput("zipcode", label="Enter your zipcode.", value = 98125)
                 
    )  ) , 
  
  
  server <- function(input, output, session) {
    zipcode <- reactive(input$zipcode)
    zipcode_d <- debounce(zipcode, millis = 2000)
    observeEvent(zipcode_d(),{     #limits zipcode input to 5 numbers only
      if(nchar(zipcode_d())!=5)
      {
        updateTextInput(session,'zipcode',value=98125)
        showModal(modalDialog(
          title = "Error!",
          "Only 5-character entries are permitted.",
          easyClose = TRUE
        ))
      }
      if(is.na(as.numeric(zipcode_d())))
      {
        showModal(modalDialog(
          title = "Error!",
          "Only numeric values are allowed. Please try again.",
          easyClose = TRUE
        ))
      }
    }
    )
  })