Register a hook that runs when a snapshot is taken

snap_on_save() registers a function that snap_take() calls after the inputs and tracked values have been collected. It receives a state object: state$inputs is the named list of captured input values and state$values is an environment. Anything the hook assigns into state$values is stored in the snapshot's values section, so several hooks (and several modules) can contribute without overwriting each other, just like shiny's onBookmark().

Usage

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

Arguments

fn

A function taking one argument, state.

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 hook sees only the module's inputs (with the namespace prefix removed) and its values are stored under namespaced names automatically.

Examples

if (interactive()) {
  library(shiny)

  server <- function(input, output, session) {
    snap_on_save(function(state) {
      state$values$fitted_at <- format(Sys.time())
    })
  }
}