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Wrap a message handler to run asynchronously with zero configuration

Source: R/async.R
async.Rd

async() is the simplest way to make an RDesk message handler non-blocking. Wrap any handler function with async() and RDesk automatically handles background execution, loading states, error toasts, and result routing.

async() transforms a standard RDesk message handler into a background task. The UI remains responsive while the task runs. When finished, a result message (e.g., get_data_result) is automatically sent back to the UI.

Usage

async(
  fn,
  app = NULL,
  loading_message = "Working...",
  cancellable = TRUE,
  error_message = "Error: "
)

Arguments

fn

The handler function, taking a payload argument.

app

The RDesk App instance. If NULL, tries to resolve from the global registry.

loading_message

Message to display in the UI overlay while working.

cancellable

Whether the UI should show a 'Cancel' button.

error_message

Prefix for toast notifications if the task fails.

Value

A wrapped handler function suitable for app$on_message().

Details

To ensure the background worker has access to all application logic, RDesk automatically sources every .R file in the application's R/ directory before executing the task. It also snapshots currently loaded packages (excluding system packages) to recreate the environment.

Examples

if (interactive()) {
  app$on_message("filter_cars", async(function(payload) {
    mtcars[mtcars$cyl == payload$cylinders, ]
  }, app = app))
}