在更改输入值时，不要删除(用户输入的)反应性变量的值。

Question

我想收集个人信息(姓名和年龄)作为用户输入附带的演示代码。初始个体数为1，当用户增加/减少个体数的值时，它将响应地添加/减少相应的行以收集单个信息。我的问题是，在增加/减少个人数量时，如何避免删除当前的输入信息。例如，屏幕快照1显示用户(me)输入的个人1的信息。当我将个人数量的值改为2时，我之前输入的信息被删除了(屏幕截图2)，我不得不重新输入个人1的信息。当我将个人数量增加到2时，我期望的是屏幕截图3 (个人1的信息不会被删除)。有人能帮我吗？谢谢!

更新05/15/2022

使用isolate的更新答案是我正在寻找的。再次感谢@jpdugo17 17的帮助。

示例代码

library(shiny)
ui <- fluidPage(
  tabsetPanel(
    tabPanel(
      h4("Individual Information"),
      fluidRow(column(4,numericInput("ninds",
                                     label = "Number of individuals",
                                     value = 1, min = 1, step = 0.5, width = "300px"))),
      br(),
      fluidRow(column(2,align = "center",strong("Individual #")),
               column(5,align = "center",strong("Individual Name")),
               column(5,align = "center",strong("Age"))),
      fluidRow(
        column(2,wellPanel(uiOutput("indNum"))),
        column(5,wellPanel(uiOutput("Name"))),
        column(5,wellPanel(uiOutput("Age"))))
    )
  )
)

server <- function(input, output) {
  # create reactive variable paste0("individualNum", i) for further using
  output$indNum <- renderUI({
    num <- as.integer(input$ninds)
    req(num)
    lapply(1:num, function(i) {
      numericInput(paste0("individualNum", i), value = i, label = "", max = i, min = i)
    })
  })
  # create reactive variable paste0("name", i) for further using 
  output$Name <- renderUI({
    num <- as.integer(input$ninds)
    req(num)
    lapply(1:num, function(i) {
      textInput(paste0("name", i), label = "")
    })
  })
  # create reactie variable paste0("age", i) for further using 
  output$Age <- renderUI({
    num <- as.integer(input$ninds)
    req(num)
    lapply(1:num, function(i) {
      numericInput(paste0("age", i), label = "", value = 0)
    })
  })
}

# Run the app ----
shinyApp(ui, server)

screenshot-1

screenshot-2

screenshot-3

​

Answer 1

编辑

我们可以将isolate与输入的当前值一起使用，并将其作为numericInput或textInput中的value参数传递。这将起作用，因为还不存在的任何输入都会产生NULL。

server <- function(input, output) {
  # create reactive variable paste0("individualNum", i) for further using

  num <- reactive({
    req(input$ninds)
    input$ninds
  })

  output$indNum <- renderUI({
    lapply(1:num(), function(i) {
      numericInput(paste0("individualNum", i), value = i, label = "", max = i, min = i)
    })
  })
  # create reactive variable paste0("name", i) for further using
  output$Name <- renderUI({
    lapply(1:num(), function(i) {
      textInput(paste0("name", i), label = "", value = isolate(input[[paste0("name", i)]]))
    })
  })
  # create reactie variable paste0("age", i) for further using
  output$Age <- renderUI({
    lapply(1:num(), function(i) {
      numericInput(paste0("age", i), label = "", value = isolate(input[[paste0("age", i)]]))
    })
  })
}

使用insertUI的原始答案

我们可以实现这样的逻辑:创建一个计数器来存储当前的输入编号，制作两个按钮，一个按钮添加，另一个按钮删除输入。我们必须用一个带有唯一id的div包装每个输入(因为输入函数通常会添加多个元素)。

library(shiny)
library(purrr)

ui <- fluidPage(
  tabsetPanel(
    tabPanel(
      h4("Individual Information"),
      fluidRow(
        column(
          4, fluidRow(
            column(6, numericInput("ninds",
              label = "Number of individuals",
              value = 1, min = 1, step = 0.5, width = "300px"
            )), column(3, actionButton("add_ui", "Add Individual", style = "background-color: green;")),
            column(3, actionButton("remove_ui", "Remove Individual", style = "background-color: red;"))
          )
        )
      ),
      br(),
      fluidRow(
        column(2, align = "center", strong("Individual #")),
        column(5, align = "center", strong("Individual Name")),
        column(5, align = "center", strong("Age"))
      ),
      fluidRow(
        column(2, wellPanel(id = "IndNumber")),
        column(5, wellPanel(id = "Name")),
        column(5, wellPanel(id = "Age"))
      )
    )
  )
)


server <- function(input, output) {

  # track the number of inputs
  ui_counter <- reactiveVal(1)

  observeEvent(input$add_ui, {
    div_nms <- map_chr(c("individualNum", "name", "age"), ~ paste0("div", .x, ui_counter()))

    # individual number
    insertUI(
      selector = "#IndNumber",
      ui = div(
        id = div_nms[[1]],
        numericInput(paste0("individualNum", ui_counter()),
          label = "",
          value = ui_counter(),
          min   = ui_counter(),
          max   = ui_counter()
        )
      )
    )

    # name input
    insertUI(
      selector = "#Name",
      ui = div(id = div_nms[[2]], textInput(paste0("name", ui_counter()),
        label = ""
      ))
    )

    # age input
    insertUI(
      selector = "#Age",
      ui = div(id = div_nms[[3]], numericInput(paste0("age", ui_counter()),
        label = "",
        value = 0
      ))
    )


    ui_counter(ui_counter() + 1)
  })

  # observer to remove the divs containing the inputs
  observeEvent(input$remove_ui, {
    if (ui_counter() > 1) {
      walk(c("individualNum", "name", "age"), ~ removeUI(paste0("#div", .x, ui_counter() - 1)))
      ui_counter(ui_counter() - 1)
    }
  })
}

# Run the app ----
shinyApp(ui, server)