我正在深入研究 Django 的通用视图，弄清楚它们如何返回一个简单的 HttpResponse 对象，就像一个简单的视图函数一样。
我编写了一个简单的测试项目，并在 django/views/generic/base.py 文件中定义的基本视图类中添加了一些日志记录命令，这样我就可以跟踪幕后发生的事情。
我在研究过程中遇到了一些问题。
然而，我一直试图保持这篇文章的简短，为了全面理解，我认为包含代码片段和日志是必不可少的。
我将非常感谢任何花时间提供一些有用评论的人，可能会回答我的一些问题。
网址.py
from django.conf.urls import patterns, url
from views import WelcomeView
urlpatterns = patterns('',
url(r'^welcome/(?P<name>\w+)/$', WelcomeView.as_view()),
)
视图.py
from django.http import HttpResponse
from django.views.generic import View
class WelcomeView(View):
def get(self, request, name):
return HttpResponse('What is up, {0}?'.format(name))
django/views/generic/base.py
class View(object):
"""
Intentionally simple parent class for all views. Only implements
dispatch-by-method and simple sanity checking.
"""
http_method_names = ['get', 'post', 'put', 'delete', 'head', 'options', 'trace']
def __init__(self, **kwargs):
#####logging
logging.error('*** View.__init__ is started with kwargs: {0} ***'.format(
repr(kwargs)))
"""
Constructor. Called in the URLconf; can contain helpful extra
keyword arguments, and other things.
"""
# Go through keyword arguments, and either save their values to our
# instance, or raise an error.
for key, value in kwargs.iteritems():
setattr(self, key, value)
#####logging
logging.error('*** View.__init__ reached its end. No return value. ***')
@classonlymethod
def as_view(cls, **initkwargs):
#####logging
logging.error('*** View.as_view is started with initkwargs: {0} ***'.format(
repr(initkwargs)))
"""
Main entry point for a request-response process.
"""
# sanitize keyword arguments
for key in initkwargs:
if key in cls.http_method_names:
raise TypeError(u"You tried to pass in the %s method name as a "
u"keyword argument to %s(). Don't do that."
% (key, cls.__name__))
if not hasattr(cls, key):
raise TypeError(u"%s() received an invalid keyword %r" % (
cls.__name__, key))
def view(request, *args, **kwargs):
#####logging
logging.error('*** View.as_view.view is called with args: {0};\
and kwargs: {1} ***'.format(
repr(args),
repr(kwargs)))
self = cls(**initkwargs)
if hasattr(self, 'get') and not hasattr(self, 'head'):
self.head = self.get
#####logging
logging.error('*** View.as_view.view reached its end.\
Now calls dispatch() and returns the return value.')
return self.dispatch(request, *args, **kwargs)
# take name and docstring from class
update_wrapper(view, cls, updated=())
# and possible attributes set by decorators
# like csrf_exempt from dispatch
update_wrapper(view, cls.dispatch, assigned=())
#####logging
logging.error('*** View.as_view reached its end. Now returns view. ***')
return view
def dispatch(self, request, *args, **kwargs):
# Try to dispatch to the right method; if a method doesn't exist,
# defer to the error handler. Also defer to the error handler if the
# request method isn't on the approved list.
#####logging
logging.error('*** View.dispatch called, with args: {0};\
and kwargs: {1} ***'.format(
repr(args),
repr(kwargs)))
if request.method.lower() in self.http_method_names:
handler = getattr(self, request.method.lower(), self.http_method_not_allowed)
else:
handler = self.http_method_not_allowed
self.request = request
self.args = args
self.kwargs = kwargs
#####logging
logging.error('*** View.dispatch reached its end.\
Now calls handler and returns the return value. ***')
return handler(request, *args, **kwargs)
def http_method_not_allowed(self, request, *args, **kwargs):
allowed_methods = [m for m in self.http_method_names if hasattr(self, m)]
logger.warning('Method Not Allowed (%s): %s', request.method, request.path,
extra={
'status_code': 405,
'request': self.request
}
)
return http.HttpResponseNotAllowed(allowed_methods)
一些测试请求的日志
Django version 1.4.5, using settings 'try1.settings'
Development server is running at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
ERROR:root:*** View.as_view is started with initkwargs: {} ***
ERROR:root:*** View.as_view reached its end. Now returns view. ***
ERROR:root:*** View.as_view.view is called with args: (); and kwargs: {'name': u'Dude'} ***
ERROR:root:*** View.__init__ is started with kwargs: {} ***
ERROR:root:*** View.__init__ reached its end. No return value. ***
ERROR:root:*** View.as_view.view reached its end. Now calls dispatch() and returns the return value.
ERROR:root:*** View.dispatch called, with args: (); and kwargs: {'name': u'Dude'} ***
ERROR:root:*** View.dispatch reached its end. Now calls handler and returns the return value. ***
[24/Feb/2013 12:43:19] "GET /welcome/Dude/ HTTP/1.1" 200 17
ERROR:root:*** View.as_view.view is called with args: (); and kwargs: {'name': u'Dude'} ***
ERROR:root:*** View.__init__ is started with kwargs: {} ***
ERROR:root:*** View.__init__ reached its end. No return value. ***
ERROR:root:*** View.as_view.view reached its end. Now calls dispatch() and returns the return value.
ERROR:root:*** View.dispatch called, with args: (); and kwargs: {'name': u'Dude'} ***
ERROR:root:*** View.dispatch reached its end. Now calls handler and returns the return value. ***
[24/Feb/2013 12:43:32] "GET /welcome/Dude/ HTTP/1.1" 200 17
[24/Feb/2013 12:44:43] "GET /welcome/ HTTP/1.1" 404 1939
ERROR:root:*** View.as_view.view is called with args: (); and kwargs: {'name': u'Bro'} ***
ERROR:root:*** View.__init__ is started with kwargs: {} ***
ERROR:root:*** View.__init__ reached its end. No return value. ***
ERROR:root:*** View.as_view.view reached its end. Now calls dispatch() and returns the return value.
ERROR:root:*** View.dispatch called, with args: (); and kwargs: {'name': u'Bro'} ***
ERROR:root:*** View.dispatch reached its end. Now calls handler and returns the return value. ***
[24/Feb/2013 12:44:59] "GET /welcome/Bro/ HTTP/1.1" 200 16
毕竟我的问题
1
、根据日志，as_view是在View.init之前调用的。
这是否意味着它甚至在创建 View 实例之前就调用了 View 方法？
2.
as_view()为什么第一次调用执行后不调用？
我还不是 Python 的导入、编译和内存使用方面的专家，
但我有一种感觉，它们在这里发挥了一些作用。
3
、在view()的定义中，下面的代码片段做了什么？
self = cls(**initkwargs)
根据日志，它触发了 View.init。
是不是它用initkwargs创建了一个新的View实例并将其分配给正在使用的实例（self）？
如果是这样，为什么需要它？
4.
我们如何利用 initkwargs（as_view 的参数）？