Save-state button and its download handler — snap_download

snap_download_button() is a downloadButton() with the client script attached. snap_download_handler() defines the matching download: it takes a snapshot with snap_take() when the button is clicked and writes it with snap_write(). Together they replace the usual downloadHandler() boilerplate.

Usage

snap_download_button(
  id,
  label = "Save state",
  icon = shiny::icon("download"),
  class = NULL,
  ...
)

snap_download_handler(
  id,
  filename = "state",
  format = c("json", "zip"),
  ...,
  snapshot = NULL,
  session = shiny::getDefaultReactiveDomain()
)

Arguments

id: The output id of the button. snap_download_handler() accepts a vector of ids, so that several buttons (for example one per tab) share one definition.
label, icon, class, ...: Passed on to shiny::downloadButton(). In snap_download_handler(), ... is passed on to snap_take().
filename: The file name without extension: a string, a function, or a reactive (for example a text input where the user names the file). It is reduced to the characters A-Z a-z 0-9 . _ -, falls back to "state" when empty, and gets the format's extension appended.
format: The file format: "json" (the default) or "zip" for a bundle that includes uploaded files (see snap_write()).
snapshot: NULL to take a snapshot when the button is clicked (the default), a snapshot object, or a function or reactive returning one.
session: The Shiny session. Defaults to the current session.

Value

snap_download_button() returns a tag. snap_download_handler() returns the ids invisibly.

Examples

if (interactive()) {
  library(shiny)

  ui <- fluidPage(
    sliderInput("n", "n", 1, 100, 50),
    textInput("filename", "File name", "state"),
    snap_download_button("save")
  )

  server <- function(input, output, session) {
    snap_enable(app = "demo", version = "1.0.0", exclude = "^filename$")
    snap_download_handler("save", filename = reactive(input$filename))
  }

  shinyApp(ui, server)
}