R Shiny：有条件地要求用户使用 select 选择器输入

Question

I have two pickerInput values in the app. In the first, geography , the user can select to view either state (default) or county data. If the user selects county , I'd like to require that they pick a state from the second pickerInput , which is just a list of states. It is not required that the user pick a state when input$geography == "state" .

I have considered putting this inside of a modalDialogue but it wasn't working. I also tried an updatePickerInput which didn't work either.

What is the best way of conditionally requiring the user to select a value from a pickerInput ?

Thank you.

Answer 1

Here is a solution with shinyjs :

library(shiny)
library(shinyWidgets)
library(shinyjs)

ui <- fluidPage(

  useShinyjs(),

  pickerInput("pick_1", choices = c("state","county"), multiple = FALSE, selected = "state"),
  shinyjs::hidden(
    pickerInput("pick_2", choices = state.name, multiple = TRUE)
  )


)

server <- function(input, output, session) {

  observe({
    toggleElement("pick_2", condition = input$pick_1 == "state")

  })


}

shinyApp(ui, server)