R/view_ui.R

In shinyobjects: Access Reactive Data Interactively

#' Show UI output in viewer pane
#'
#' @param x ui content (actionButton, selectInput, valueBox), if x is not provided, \code{view_ui()} will look for selected text in the source pane or the last output from running the UI code. In the latter case, it expects an object with class "shiny.tag" or "shiny.tag.list"
#' @param close_after number of seconds to display UI in Viewer panel. If NULL, app must be stopped manually before more code can be run.
#' @importFrom shiny shinyApp fluidPage runApp stopApp
#' @importFrom rstudioapi viewer getSourceEditorContext
#' @importFrom utils menu
#' @export
#' @examples 
#' if (interactive()) {
#' # run this line
#' shiny::selectInput(
#'   "state",
#'   "Choose a state:",
#'   list(
#'     `East Coast` = list("NY", "NJ", "CT"),
#'     `West Coast` = list("WA", "OR", "CA"),
#'     `Midwest` = list("MN", "WI", "IA")
#'   )
#' )
#' # the output will automatically be used here
#' view_ui(close_after = 6)
#' }
#' 
view_ui <- function(x, close_after = 5) {
  # nocov start
  if (missing(x)) {
    selected_text <- rstudioapi::getSourceEditorContext()$selection[[1]]$text
    if (nchar(selected_text) > 1) {
      res <- 
        menu(
          choices = c("Yes", "No"), 
          title = "Do you want to use the selected text from the source pane?"
        )
      if (res == 1) x <- eval(parse(text = selected_text))
      if (res == 2) x <- .Last.value
    } else {
      x <- .Last.value 
    }
  }
  # nocov end
  
  if (!class(x)[1] %in% c("shiny.tag", "shiny.tag.list")) {
    message(
      paste(
        'if output is not what you expected, view_ui() expects',
        '"shiny.tag" or "shiny.tag.list"'
      )
    )
  }
  
  ui <- fluidPage(x)
  
  server <- function(input, output) {
    # nocov start
    if (!is.null(close_after)) {
      Sys.sleep(close_after)
      stopApp()
    }
    # nocov end
  }
  
  app <- shinyApp(ui, server)
  
  runApp(
    appDir = app, 
    launch.browser = rstudioapi::viewer
  )
}