# Τεκμηρίωση του Django - 1.10.7

# Base views

The following three classes provide much of the functionality needed to create Django views. You may think of them as parent views, which can be used by themselves or inherited from. They may not provide all the capabilities required for projects, in which case there are Mixins and Generic class-based views.

Many of Django’s built-in class-based views inherit from other class-based views or various mixins. Because this inheritance chain is very important, the ancestor classes are documented under the section title of Ancestors (MRO). MRO is an acronym for Method Resolution Order.

## `View`

class `django.views.generic.base.``View`

  The master class-based base view. All other class-based views inherit from this base class. It isn’t strictly a generic view and thus can also be imported from `django.views`.

  The ability to import from `django.views` was added.

  Method Flowchart

  1. `dispatch()`
  2. `http_method_not_allowed()`
  3. `options()`

  Example views.py:

      from django.http import HttpResponse
      from django.views import View

      class MyView(View):

          def get(self, request, *args, **kwargs):
              return HttpResponse('Hello, World!')

  Example urls.py:

      from django.conf.urls import url

      from myapp.views import MyView

      urlpatterns = [
          url(r'^mine/$', MyView.as_view(), name='my-view'),
      ]

  Attributes

  `http_method_names`

    The list of HTTP method names that this view will accept.

    Default:

        ['get', 'post', 'put', 'patch', 'delete', 'head', 'options', 'trace']

  Methods

  classmethod `as_view`(**initkwargs)

    Returns a callable view that takes a request and returns a response:

        response = MyView.as_view()(request)

    The returned view has `view_class` and `view_initkwargs` attributes.

  `dispatch`(request, *args, **kwargs)

    The `view` part of the view – the method that accepts a `request` argument plus arguments, and returns a HTTP response.

    The default implementation will inspect the HTTP method and attempt to delegate to a method that matches the HTTP method; a `GET` will be delegated to `get()`, a `POST` to `post()`, and so on.

    By default, a `HEAD` request will be delegated to `get()`. If you need to handle `HEAD` requests in a different way than `GET`, you can override the `head()` method. See Supporting other HTTP methods for an example.

  `http_method_not_allowed`(request, *args, **kwargs)

    If the view was called with a HTTP method it doesn’t support, this method is called instead.

    The default implementation returns `HttpResponseNotAllowed` with a list of allowed methods in plain text.

  `options`(request, *args, **kwargs)

    Handles responding to requests for the OPTIONS HTTP verb. Returns a response with the `Allow` header containing a list of the view’s allowed HTTP method names.

## `TemplateView`

class `django.views.generic.base.``TemplateView`

  Renders a given template, with the context containing parameters captured in the URL.

  Ancestors (MRO)

  This view inherits methods and attributes from the following views:

  - `django.views.generic.base.TemplateResponseMixin`
  - `django.views.generic.base.ContextMixin`
  - `django.views.generic.base.View`

  Method Flowchart

  1. `dispatch()`
  2. `http_method_not_allowed()`
  3. `get_context_data()`

  Example views.py:

      from django.views.generic.base import TemplateView

      from articles.models import Article

      class HomePageView(TemplateView):

          template_name = "home.html"

          def get_context_data(self, **kwargs):
              context = super(HomePageView, self).get_context_data(**kwargs)
              context['latest_articles'] = Article.objects.all()[:5]
              return context

  Example urls.py:

      from django.conf.urls import url

      from myapp.views import HomePageView

      urlpatterns = [
          url(r'^$', HomePageView.as_view(), name='home'),
      ]

  Context

  - Populated (through `ContextMixin`) with the keyword arguments captured from the URL pattern that served the view.

## `RedirectView`

class `django.views.generic.base.``RedirectView`

  Redirects to a given URL.

  The given URL may contain dictionary-style string formatting, which will be interpolated against the parameters captured in the URL. Because keyword interpolation is always done (even if no arguments are passed in), any `"%"` characters in the URL must be written as `"%%"` so that Python will convert them to a single percent sign on output.

  If the given URL is `None`, Django will return an `HttpResponseGone` (410).

  Ancestors (MRO)

  This view inherits methods and attributes from the following view:

  - `django.views.generic.base.View`

  Method Flowchart

  1. `dispatch()`
  2. `http_method_not_allowed()`
  3. `get_redirect_url()`

  Example views.py:

      from django.shortcuts import get_object_or_404
      from django.views.generic.base import RedirectView

      from articles.models import Article

      class ArticleCounterRedirectView(RedirectView):

          permanent = False
          query_string = True
          pattern_name = 'article-detail'

          def get_redirect_url(self, *args, **kwargs):
              article = get_object_or_404(Article, pk=kwargs['pk'])
              article.update_counter()
              return super(ArticleCounterRedirectView, self).get_redirect_url(*args, **kwargs)

  Example urls.py:

      from django.conf.urls import url
      from django.views.generic.base import RedirectView

      from article.views import ArticleCounterRedirectView, ArticleDetail

      urlpatterns = [
          url(r'^counter/(?P<pk>[0-9]+)/$', ArticleCounterRedirectView.as_view(), name='article-counter'),
          url(r'^details/(?P<pk>[0-9]+)/$', ArticleDetail.as_view(), name='article-detail'),
          url(r'^go-to-django/$', RedirectView.as_view(url='https://djangoproject.com'), name='go-to-django'),
      ]

  Attributes

  `url`

    The URL to redirect to, as a string. Or `None` to raise a 410 (Gone) HTTP error.

  `pattern_name`

    The name of the URL pattern to redirect to. Reversing will be done using the same args and kwargs as are passed in for this view.

  `permanent`

    Whether the redirect should be permanent. The only difference here is the HTTP status code returned. If `True`, then the redirect will use status code 301. If `False`, then the redirect will use status code 302. By default, `permanent` is `False`.

    The default value of the `permanent` attribute changed from `True` to `False`.

  `query_string`

    Whether to pass along the GET query string to the new location. If `True`, then the query string is appended to the URL. If `False`, then the query string is discarded. By default, `query_string` is `False`.

  Methods

  `get_redirect_url`(*args, **kwargs)

    Constructs the target URL for redirection.

    The default implementation uses `url` as a starting string and performs expansion of `%` named parameters in that string using the named groups captured in the URL.

    If `url` is not set, `get_redirect_url()` tries to reverse the `pattern_name` using what was captured in the URL (both named and unnamed groups are used).

    If requested by `query_string`, it will also append the query string to the generated URL. Subclasses may implement any behavior they wish, as long as the method returns a redirect-ready URL string.