Revision Log

06_aspects.py

Revision 130 (checked in by rdelon, 4 years ago)	--

Line
1	"""
2	Tutorial 06 - Aspects
3
4	CherryPy2 aspects let you dynamically alter a request handler object's
5	behaviour by adding code that gets executed before and/or after
6	requested methods. This is useful in situations where you need common
7	method behavior across multiple methods or even objects (aspects can
8	be part of derived classes).
9	"""
10
11	from cherrypy import cpg
12
13	# We need to import some additional stuff for our aspect code.
14	from cherrypy.lib.aspect import Aspect, STOP, CONTINUE
15
16
17	class Page(Aspect):
18	title = 'Untitled Page'
19
20	def header(self):
21	# this is the same as in tutorial05.py
22	return '''
23	<html>
24	<head>
25	<title>%s</title>
26	<head>
27	<body>
28	<h2>%s</h2>
29	''' % (self.title, self.title)
30
31	def footer(self):
32	# this is the same as in tutorial05.py
33	return '''
34	</body>
35	</html>
36	'''
37
38	def _before(self, methodName, method):
39	# The _before aspect method gets executed whenever any
40	# other method is called, including header and footer -- which
41	# is something we don't want, so we check the called method
42	# first.
43	if methodName not in ['header', 'footer']:
44	return CONTINUE, self.header()
45	else:
46	return CONTINUE, ''
47
48	def _after(self, methodName, method):
49	# Same as above, except _after gets called after the actually
50	# requested method was executed. Its results are appended to
51	# the output string.
52	if getattr(method, 'exposed', False) and methodName not in ['header', 'footer']:
53	return CONTINUE, self.footer()
54	else:
55	# If the method is not exposed or if it's the header and footer itself,
56	# don't do anything
57	return CONTINUE, ''
58
59
60
61	class HomePage(Page):
62	title = 'Tutorial 6 -- Aspect Powered!'
63
64	def __init__(self):
65	self.another = AnotherPage()
66
67	def index(self):
68	# Note that we don't call the header and footer methods
69	# anymore! The aspect methods inherited from the Page class
70	# take care of that now.
71	return '''
72	<p>
73	Isn't this exciting? There's
74	<a href="./another/">another page</a>, too!
75	</p>
76	'''
77
78	index.exposed = True
79
80
81	class AnotherPage(Page):
82	title = 'Another Page'
83
84	def index(self):
85	# See above. No header or footer methods called!
86	return '''
87	<p>
88	And this is the amazing second page!
89	</p>
90	'''
91
92	index.exposed = True
93
94
95	cpg.root = HomePage()
96
97	cpg.server.start(configFile = 'tutorial.conf')

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