Restore-state upload and its handler

snap_file_input() is a fileInput() with the client script attached. snap_file_restore() observes it: when a file is uploaded it reads the snapshot with snap_read(), runs validate and migrate, and calls snap_restore(), reporting problems to the user.

Usage

snap_file_input(id, label = "Restore state", accept = c(".json", ".zip"), ...)

snap_file_restore(
  id,
  ...,
  validate = NULL,
  migrate = NULL,
  on_error = c("notify", "modal", "stop"),
  session = shiny::getDefaultReactiveDomain()
)

Arguments

id

The input id. snap_file_restore() accepts a vector of ids, so that several upload controls share one definition.

label, accept, ...

Passed on to shiny::fileInput(). In snap_file_restore(), ... is passed on to snap_restore().

validate

A function of the snapshot that should stop() with a user-facing message when the file is not acceptable. Runs first.

migrate

A function function(snapshot, from_version) returning a modified snapshot, for example filling in defaults for values introduced after from_version (the app version recorded in the file, or NULL). Runs after validate, before anything is touched.

on_error

How to report a file that cannot be restored: a showNotification() (the default), a showModal() dialog, or stop().

session

The Shiny session. Defaults to the current session.

Value

snap_file_input() returns a tag. snap_file_restore() returns the ids invisibly.

Examples

if (interactive()) {
  library(shiny)

  ui <- fluidPage(
    sliderInput("n", "n", 1, 100, 50),
    snap_download_button("save"),
    snap_file_input("restore")
  )

  server <- function(input, output, session) {
    snap_enable(app = "demo", version = "1.0.0")
    snap_download_handler("save")
    snap_file_restore("restore", validate = function(snap) {
      if (is.null(snap$inputs$n)) stop("This file does not contain `n`.")
    })
  }

  shinyApp(ui, server)
}