1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
|
# -*- coding: utf-8 -*-
"""
flask.views
~~~~~~~~~~~
This module provides class-based views inspired by the ones in Django.
:copyright: 2010 Pallets
:license: BSD-3-Clause
"""
from ._compat import with_metaclass
from .globals import request
http_method_funcs = frozenset(
["get", "post", "head", "options", "delete", "put", "trace", "patch"]
)
class View(object):
"""Alternative way to use view functions. A subclass has to implement
:meth:`dispatch_request` which is called with the view arguments from
the URL routing system. If :attr:`methods` is provided the methods
do not have to be passed to the :meth:`~flask.Flask.add_url_rule`
method explicitly::
class MyView(View):
methods = ['GET']
def dispatch_request(self, name):
return 'Hello %s!' % name
app.add_url_rule('/hello/<name>', view_func=MyView.as_view('myview'))
When you want to decorate a pluggable view you will have to either do that
when the view function is created (by wrapping the return value of
:meth:`as_view`) or you can use the :attr:`decorators` attribute::
class SecretView(View):
methods = ['GET']
decorators = [superuser_required]
def dispatch_request(self):
...
The decorators stored in the decorators list are applied one after another
when the view function is created. Note that you can *not* use the class
based decorators since those would decorate the view class and not the
generated view function!
"""
#: A list of methods this view can handle.
methods = None
#: Setting this disables or force-enables the automatic options handling.
provide_automatic_options = None
#: The canonical way to decorate class-based views is to decorate the
#: return value of as_view(). However since this moves parts of the
#: logic from the class declaration to the place where it's hooked
#: into the routing system.
#:
#: You can place one or more decorators in this list and whenever the
#: view function is created the result is automatically decorated.
#:
#: .. versionadded:: 0.8
decorators = ()
def dispatch_request(self):
"""Subclasses have to override this method to implement the
actual view function code. This method is called with all
the arguments from the URL rule.
"""
raise NotImplementedError()
@classmethod
def as_view(cls, name, *class_args, **class_kwargs):
"""Converts the class into an actual view function that can be used
with the routing system. Internally this generates a function on the
fly which will instantiate the :class:`View` on each request and call
the :meth:`dispatch_request` method on it.
The arguments passed to :meth:`as_view` are forwarded to the
constructor of the class.
"""
def view(*args, **kwargs):
self = view.view_class(*class_args, **class_kwargs)
return self.dispatch_request(*args, **kwargs)
if cls.decorators:
view.__name__ = name
view.__module__ = cls.__module__
for decorator in cls.decorators:
view = decorator(view)
# We attach the view class to the view function for two reasons:
# first of all it allows us to easily figure out what class-based
# view this thing came from, secondly it's also used for instantiating
# the view class so you can actually replace it with something else
# for testing purposes and debugging.
view.view_class = cls
view.__name__ = name
view.__doc__ = cls.__doc__
view.__module__ = cls.__module__
view.methods = cls.methods
view.provide_automatic_options = cls.provide_automatic_options
return view
class MethodViewType(type):
"""Metaclass for :class:`MethodView` that determines what methods the view
defines.
"""
def __init__(cls, name, bases, d):
super(MethodViewType, cls).__init__(name, bases, d)
if "methods" not in d:
methods = set()
for base in bases:
if getattr(base, "methods", None):
methods.update(base.methods)
for key in http_method_funcs:
if hasattr(cls, key):
methods.add(key.upper())
# If we have no method at all in there we don't want to add a
# method list. This is for instance the case for the base class
# or another subclass of a base method view that does not introduce
# new methods.
if methods:
cls.methods = methods
class MethodView(with_metaclass(MethodViewType, View)):
"""A class-based view that dispatches request methods to the corresponding
class methods. For example, if you implement a ``get`` method, it will be
used to handle ``GET`` requests. ::
class CounterAPI(MethodView):
def get(self):
return session.get('counter', 0)
def post(self):
session['counter'] = session.get('counter', 0) + 1
return 'OK'
app.add_url_rule('/counter', view_func=CounterAPI.as_view('counter'))
"""
def dispatch_request(self, *args, **kwargs):
meth = getattr(self, request.method.lower(), None)
# If the request method is HEAD and we don't have a handler for it
# retry with GET.
if meth is None and request.method == "HEAD":
meth = getattr(self, "get", None)
assert meth is not None, "Unimplemented method %r" % request.method
return meth(*args, **kwargs)
|
