Helpers

Helpers are methods that plugins can expose to other plugins in order to make common functionality available on the system. They are registered with the OctoPrint plugin system through the use of the control property __plugin_helpers__.

An example for providing some helper functions to the system can be found in the bundled Discovery Plugin which provides its SSDP browsing and Zeroconf browsing and publishing functions as helper methods.

src/octoprint/plugins/discovery/__init__.py

def __plugin_load__():
    plugin = DiscoveryPlugin()

    global __plugin_implementation__
    __plugin_implementation__ = plugin

    global __plugin_helpers__
    __plugin_helpers__ = {
        "ssdp_browse": plugin.ssdp_browse,
        "zeroconf_browse": plugin.zeroconf_browse,
        "zeroconf_register": plugin.zeroconf_register,
        "zeroconf_unregister": plugin.zeroconf_unregister,
    }

An example of how to use helpers can be found in the (unmaintained) Growl Plugin. Using octoprint.plugin.core.PluginManager.get_helpers plugins can retrieve exported helper methods and call them as (hopefully) documented.

def on_after_startup(self):
    host = self._settings.get(["hostname"])
    port = self._settings.getInt(["port"])
    password = self._settings.get(["password"])

    helpers = self._plugin_manager.get_helpers("discovery", "zeroconf_browse")
    if helpers and "zeroconf_browse" in helpers:
        self.zeroconf_browse = helpers["zeroconf_browse"]

    self.growl, _ = self._register_growl(host, port, password=password)

# [...]

def on_api_get(self, request):
    if not self.zeroconf_browse:
        return flask.jsonify(dict(
            browsing_enabled=False
        ))

    browse_results = self.zeroconf_browse("_gntp._tcp", block=True)
    growl_instances = [dict(name=v["name"], host=v["host"], port=v["port"]) for v in browse_results]

    return flask.jsonify(dict(
        browsing_enabled=True,
        growl_instances=growl_instances
    ))