Register hooks that run around a restore

snap_on_restore() registers a function that snap_restore() calls after the tracked values have been written back and before the input values are sent to the browser. snap_on_restored() registers a function that runs once the browser reports that the restore has settled. Both receive a state list with inputs (the named list of input values being restored), values (the values section of the file), snapshot (the whole snapshot), and txn (the transaction id); the restored hook also receives the restore report.

Usage

snap_on_restore(fn, session = shiny::getDefaultReactiveDomain())

snap_on_restored(fn, session = shiny::getDefaultReactiveDomain())

Arguments

fn

A function taking state (and, for snap_on_restored(), report).

session

The Shiny session. Defaults to the current session.

Value

A function with no arguments that removes the hook when called.

Details

Inside a module, the hooks see only the module's inputs and values, with the namespace prefix removed, and only the module's rows of the report.

Errors raised by a hook abort the restore and reject its promise.

Examples

if (interactive()) {
  library(shiny)

  server <- function(input, output, session) {
    snap_on_restore(function(state) {
      message("restoring ", length(state$inputs), " inputs")
    })
    snap_on_restored(function(state, report) {
      print(report)
    })
  }
}