plumber2 (version 0.2.0)

api_on: Add a handler to an event

Description

During the life cycle of a plumber API various events will be fired, either automatically or manually. See the article on events in fiery for a full overview. api_on() allows you to add handlers that are called when specific events fire. api_off() can be used to remove the handler if necessary

Usage

api_on(api, event, handler, id = NULL)
api_off(api, id)

Value

These functions return the api object allowing for easy chaining with the pipe

Arguments

api

A plumber2 api object to launch or stop

event

A string naming the event to listen for

handler

A function to call when event fires

id

A string uniquely identifying the handler. If NULL a random id will be generated making it impossible to remove the handler again

Using annotation

Event handler setup doesn't have a dedicated annotation tag, but you can set it up in a @plumber block

#* @plumber
function(api) {
  api |>
    api_on("cycle-end", function(server) {
      server$log("message", "tick-tock")
    })
}

Examples

# Add a small console log to show the api is alive
pa <- api() |>
  api_on("cycle-end", function(server) {
    server$log("message", "tick-tock")
  }, id = "lifesign")

# Remove it again
pa |>
  api_off("lifesign")