selectedmethod.py

import functools
import collections

import cherrypy

__metaclass__ = type  # enable new-style classes by default


class SelectedMethod:
	"""
	Descriptor allowing a series of handler methods to satisfy
	a variety of behaviors based on the request method.

	Works similar to the MethodDispatcher, but doesn't
	require replacing the whole dispatch mechanism, so
	may be deployed selectively.

	First, decorate your method using SelectedMethod::

		class App:
			@SelectedMethod
			def index(self):
				return "Hello World"

	Then, add separate handlers for specific methods::

			@index.GET
			def get(self):
				return "Your method was GET"

			@index.POST
			def delete(self):
				db.delete(self.id)

	The first handler passed will always handle any methods
	not specified. The app may wish to
	raise 405 in this case::

			@SelectedMethod
			def index(self):
				raise cherrypy.HTTPError("405 Method Not Allowed")
	"""
	__isabstractmethod__ = False

	def __init__(self, orig):
		self.methods = collections.defaultdict(lambda: orig)

	def __get__(self, obj, type=None):
		method = self.methods[cherrypy.request.method]
		bound = functools.partial(method, obj)
		bound.exposed = True
		return bound

	def __getattr__(self, method):
		"""
		Return a decorator suitable for wrapping another
		"""
		def wrapper(func):
			self.methods[method] = func
			return func
		return wrapper