QuixoteQLookup

= Quixote _q_lookup emulation in !CherryPy 2.2 =

Courtesy of cherrypy (at) wojas.vvtp.tudelft.nl

{{{
#!python
def traverse(func):
	"""
	(Decorator)
	Desperate attempt at implementing Quixote's _q_lookup functionality in CherryPy.
	Using this decorator a default method can return an object to continue path traversal.
	Makes REST style paths like /object/123/ and /object/123/edit possible without big
	switch blocks in object's default method..
	This decorator also exposes the page.
	"""
	def wrapper(self, *args, **kwargs):
		import types
		result = func(self, *args, **kwargs)
		if isinstance(result, object) and not isinstance(result, (basestring, types.GeneratorType)):
			# do _q_lookup style directory traversal
			path = cherrypy.request.path
			if len(args)==1:
				# this is the end of the traversal
				# make sure the path ends with a /
				if not path.endswith('/'):
					raise cherrypy.HTTPRedirect(path+'/')
				# and then just call index
				m = getattr(result, 'index', None)
				if m and getattr(m, 'exposed', False):
					return m(**kwargs)
				else:
					raise cherrypy.NotFound(cherrypy.request.path+'/'+args[0])
			else:
				# still some parts to handle
				m = getattr(result, args[1], None)
				if m and getattr(m, 'exposed', False):
					if len(path)>1 and path.endswith('/'):
						# make sure the path doesn't end with a /
						raise cherrypy.HTTPRedirect(path[:-1])
					return m(*args[2:], **kwargs)
				else:
					# call 'default' method if it exists
					m = getattr(result, 'default', None)
					if m and getattr(m, 'exposed', False):
						return m(*args[1:], **kwargs)
					else:
						raise cherrypy.NotFound(cherrypy.request.path+'/'+args[1])
		else:
			# normal result, no traversal
			return result

	wrapper.exposed = True
	return wrapper
}}}

Usage:

{{{
#!python
class TraverseTest(object):

	exposed = True
	n = None

	def __init__(self, n=42):
		self.n = n

	@expose
	def show(self):
		yield "Hello from show! %s" % self.n

	@expose
	def index(self):
		yield "Hello from index! %s" % self.n

	@traverse
	def default(self, *args, **kwargs):
		try:
			i = int(args[0])
		except ValueError:
			return "'%s' is not an integer, won't traverse" % args[0]
		else:
			return TraverseTest(args[0])
}}}