TurboGears - 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