Writing Extensions

TurboGears extensions are identified by tgext.* package. A Gearbox toolkit provides tgext command to create a sample extension. For example −

gearbox tgext -n myextension

Other optional parameters for this command are −

• –author − name of package author.
• –email − email of package author.
• –licence − licence used for package. Default is MIT.
• –description − Description of package.
• –keywords − Package keywords (default: turbogears2.extension).

This will create a tgext.myextension directory, which has a simple sample extension inside.

Run the setup.py inside the directory −Python setup.py install

The _init_.py file inside tgext/myextension folder contains −

• Plugme function − This is the entry point of extension.
• SetupExtension class − extension initialization takes place here.
• On_startup function − inside the class is a hook registered on __call__ function inside class.

Brief version of the tgext\myextension\__init__.py.

from tg import config from tg import hooks from tg.configuration import milestones import logging log = logging.getLogger('tgext.myextension') def plugme(configurator, options = None): if options is None: options = {} log.info('Setting up tgext.myextension extension...') milestones.config_ready.register(SetupExtension(configurator)) return dict(appid='tgext.myextension') class SetupExtension(object): def __init__(self, configurator): self.configurator = configurator def __call__(self): log.info('>>> Public files path is %s' % config['paths']['static_files']) hooks.register('startup', self.on_startup) def echo_wrapper_factory(handler, config): def echo_wrapper(controller, environ, context): log.info('Serving: %s' % context.request.path) return handler(controller, environ, context) return echo_wrapper self.configurator.register_wrapper(echo_wrapper_factory) def on_startup(self): log.info('+ Application Running!')

Once the extension is installed, turn it on by making the following additions in the application’s app_cfg.py configuration file.

from tgext.myextension import plugme plugme(base_config)

If we launch the server using a gearbox server command, the notification of a newly registered extension can be viewed on the console by the following −

14:29:13,250 INFO [tgext.myextension] Setting up tgext.myextension extension... 14:29:13,453 INFO [tgext.myextension] >>> Public files path is c:\tghello\hello\hello\public 14:29:13,453 INFO [tgext.myextension] + Application Running! Starting Standard HTTP server on http://127.0.0.1:8080