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Django の汎用クラスビューはとても便利ではあるが、内部で何やってるか分からないので最初はハードル高い。




views.schedule_list と url を関連付ける

from django.conf.urls import patterns, include, url
import views

urlpatterns = patterns('',
    url(r'^$', views.schedule_list , name='scheduler_toppage'),

関数 views.schedule_list の処理

from django.shortcuts import render
from models import Schedule, VisitorSchedule, MemberSchedule, HelperSchedule
from datetime import datetime

def schedule_list(request):
    schedule_list = Schedule.objects.filter(event_date__gte=datetime.now()).select_related()

    for schedule in schedule_list:
        visitor_schedules = VisitorSchedule.objects.filter(schedule_id=schedule.id).select_related()
        schedule.visitor_schedules = visitor_schedules

        member_schedules = MemberSchedule.objects.filter(schedule_id=schedule.id)
        schedule.member_schedules = member_schedules

        helper_schedules = HelperSchedule.objects.filter(schedule_id=schedule.id)
        schedule.helper_schedules = helper_schedules

    return render(request, 'scheduler/schedule_list.html', {'schedule_list': schedule_list})


as_view って何?

from django.conf.urls import patterns, url, include
from django.views.generic import ListView

urlpatterns = patterns('',
    (r'^items/$', ListView.as_view()),
from django.views.generic import ListView
from sample_app.models import Item

class ItemView(ListView):
    model = Item

as_view は何をしてるのか

as_view は汎用クラスビューの基底クラスに定義されている。
以下はdjango1.9.7 のViewクラス

平たく言うと、dispatchのところで、HTTPメソッド(GETとかPOSTとか)に対応した名前のViewメソッドを呼ぶように書かれている。(GETメソッドなら、def getを呼ぶ)

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', 'patch', 'delete', 'head', 'options', 'trace']

    def __init__(self, **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 six.iteritems(kwargs):
            setattr(self, key, value)

    # このメソッドをurlと関連付ける
    def as_view(cls, **initkwargs):
        Main entry point for a request-response process.
        for key in initkwargs:
            if key in cls.http_method_names:
                raise TypeError("You tried to pass in the %s method name as a "
                                "keyword argument to %s(). Don't do that."
                                % (key, cls.__name__))
            if not hasattr(cls, key):
                raise TypeError("%s() received an invalid keyword %r. as_view "
                                "only accepts arguments that are already "
                                "attributes of the class." % (cls.__name__, key))

        def view(request, *args, **kwargs):
            self = cls(**initkwargs)
            if hasattr(self, 'get') and not hasattr(self, 'head'):
                self.head = self.get
            self.request = request
            self.args = args
            self.kwargs = kwargs
            return self.dispatch(request, *args, **kwargs)
        view.view_class = cls
        view.view_initkwargs = initkwargs

        # 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=())
        return view

    # このメソッドでHTTPリクエストに応じたViewのメソッドを呼び出すよう、定義されている
    # 例えば、GETメソッドで呼び出されたら、def getというViewクラス内のメソッドを呼び出す
    # 以下に実例を書いたので参照の事
    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.
        if request.method.lower() in self.http_method_names:
            handler = getattr(self, request.method.lower(), self.http_method_not_allowed)
            handler = self.http_method_not_allowed
        return handler(request, *args, **kwargs)

    def http_method_not_allowed(self, request, *args, **kwargs):
        logger.warning('Method Not Allowed (%s): %s', request.method, request.path,
                'status_code': 405,
                'request': request
        return http.HttpResponseNotAllowed(self._allowed_methods())

    def options(self, request, *args, **kwargs):
        Handles responding to requests for the OPTIONS HTTP verb.
        response = http.HttpResponse()
        response['Allow'] = ', '.join(self._allowed_methods())
        response['Content-Length'] = '0'
        return response

    def _allowed_methods(self):
        return [m.upper() for m in self.http_method_names if hasattr(self, m)]

HTTP GETメソッドで呼び出すと、ListViewが継承している、BaseListViewのgetメソッドが呼び出される。


class BaseListView(MultipleObjectMixin, View):
    A base view for displaying a list of objects.
    def get(self, request, *args, **kwargs):
        self.object_list = self.get_queryset()
        allow_empty = self.get_allow_empty()

        if not allow_empty:
            # When pagination is enabled and object_list is a queryset,
            # it's better to do a cheap query than to load the unpaginated
            # queryset in memory.
            if (self.get_paginate_by(self.object_list) is not None
                    and hasattr(self.object_list, 'exists')):
                is_empty = not self.object_list.exists()
                is_empty = len(self.object_list) == 0
            if is_empty:
                raise Http404(_("Empty list and '%(class_name)s.allow_empty' is False.")
                        % {'class_name': self.__class__.__name__})
        context = self.get_context_data()
        return self.render_to_response(context)

class ListView(MultipleObjectTemplateResponseMixin, BaseListView):
    Render some list of objects, set by `self.model` or `self.queryset`.
    `self.queryset` can actually be any iterable of items, not just a queryset.


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