Question

我需要在服务器端为selectInput生成选择（它们将根据数据库中的更改而更改）。如本例所示，除了在服务器端呈现整个UI元素之外，还有其他选择吗？

server <- function(input, output, session) {
  data("mtcars")
  output$select_cars = renderUI({
    selectInput("cyl",
                label = "Select cylinder",
                choices = mtcars %>% distinct(cyl) %>% pull %>% append("All", after = 0))
  })
}

ui = fluidPage(
  uiOutput("select_cars")
)

shinyApp(ui, server)

类似于在服务器端创建反应值并将其发送到UI进行渲染？如果是这样，什么是更明智的做法（或者是什么利弊）？

Answer 1

使用updateSelectInput的示例：

library(shiny)

ui <-  fluidPage(
  selectInput("column", "Select column", choices = names(mtcars)),
  selectInput("value", "", choices = NULL, multiple = TRUE),
  verbatimTextOutput("selected")
)

server <- function(input, output, session) {
  observeEvent(input$column, {
    updateSelectInput(session, "value", paste("Select", input$column, "value(s)"),
                      choices = sort(unique(mtcars[[input$column]])))
  })

  output$selected <- renderText({
    paste0(input$column, ": ", paste(input$value, collapse = ", "))
  })
}

shinyApp(ui, server)

另外，这不是OP的问题，但是我们可以看到他们正在尝试实现“全选”选项，我建议开箱即用的shinyWidgets::pickerInput()具有此功能（很好的实现）：< / p>

library(shiny)
library(shinyWidgets)

ui <-  fluidPage(
  selectInput("column", "Select column", choices = names(mtcars)),
  pickerInput("value", "", choices = NULL, multiple = TRUE, 
              options = list(`actions-box` = TRUE)),
  verbatimTextOutput("selected")
)

server <- function(input, output, session) {
  observeEvent(input$column, {
    updatePickerInput(session, "value", paste("Select", input$column, "value(s)"),
                      choices = sort(unique(mtcars[[input$column]])))
  })

  output$selected <- renderText({
    paste0(input$column, ": ", paste(input$value, collapse = ", "))
  })
}

shinyApp(ui, server)

更紧密地模仿OP的示例：

ui <-  fluidPage(
  pickerInput("cyl", "", choices = NULL, multiple = TRUE, 
              options = list(`actions-box` = TRUE))
)

server <- function(input, output, session) {
  observe({
    updatePickerInput(session, "cyl", "Select cylinder", 
                      choices = sort(unique(mtcars$cyl)))
  })
}

shinyApp(ui, server)

如果不需要反应来更新输入，甚至可以进一步简化：

server <- function(input, output, session) {
  updatePickerInput(session, "cyl", "Select cylinder", 
                    choices = sort(unique(mtcars$cyl)))
}

闪亮：uiOutput与将反应值插入selectInput

1 个答案: