更改输入值时不要清除(用户输入的)react 变量的值

Edit:

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中的值参数传递.这是可行的，因为任何尚不存在的输入都会产生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)]]))
    })
  })
}

原始答案使用insertUI:

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，一个用于添加，另一个用于删除输入.我们必须用一个具有唯一id的div来包装每个输入(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)