modal-module.R

modalContinue <- function(id) {
  ns <- NS(id)
  showModal(modalDialog(
    "This is really important!",
    "Are you sure you want to continue?",
    footer = list(
      actionButton(ns("yes"), "yes"),
      actionButton(ns("no"), "no")
    ),
    easyClose = FALSE
  ))
} 
modalContinueServer <- function(id) {
  module <- function(input, output, session) {
    val <- reactiveVal(NULL)
    observeEvent(input$yes, {
      removeModal()
      val(TRUE)
    })
    observeEvent(input$no, {
      removeModal()
      val(FALSE)
    })
    
    reactive(val())
  }
  callModule(module, id)
}

# -------------------------------------------------------------------------

ui <- fluidPage(
  actionButton("go", "Go"),
  textOutput("result")
)

server <- function(input, output, session) {
  observeEvent(input$go, {
    modalContinue("ok")
  })
  result <- modalContinueServer("ok")
  
  output$result <- renderText(result())
}
shinyApp(ui, server)