# Other Mixins

These mixins handle other random bits of Django’s views, like controlling output, controlling content types, or setting values in the context.

## SetHeadlineMixin

The `SetHeadlineMixin` allows you to statically or programmatically set the headline of any of your views. Ideally, you’ll write as few templates as possible, so a mixin like this helps you reuse generic templates. Its usage is amazingly straightforward and works much like Django’s built-in `get_queryset` method. This mixin has two ways of being used:

### Static Example

    from django.utils.translation import ugettext_lazy as _
    from django.views import TemplateView

    from braces.views import SetHeadlineMixin

    class HeadlineView(SetHeadlineMixin, TemplateView):
        headline = _(u"This is our headline")
        template_name = u"path/to/template.html"

### Dynamic Example

    from datetime import date

    from django.views import TemplateView

    from braces.views import SetHeadlineMixin

    class HeadlineView(SetHeadlineMixin, TemplateView):
        template_name = u"path/to/template.html"

        def get_headline(self):
            return u"This is our headline for {0}".format(date.today().isoformat())

For both usages, the context now contains a `headline` key with your headline.

## StaticContextMixin

Added in version 1.4.

The `StaticContextMixin` allows you to easily set static context data by using the `static_context` property.

Note

While it’s possible to override the `StaticContextMixin.get_static_context method`, it’s not very practical. If you have a need to override a method for dynamic context data it’s best to override the standard `get_context_data` method of Django’s generic class-based views.

### View Example

    # views.py

    from django.views import TemplateView

    from braces.views import StaticContextMixin

    class ContextTemplateView(StaticContextMixin, TemplateView):
        static_context = {u"nav_home": True}

### URL Example

    # urls.py

    urlpatterns = patterns(
        '',
        url(ur"^$",
            ContextTemplateView.as_view(
                template_name=u"index.html",
                static_context={u"nav_home": True}
            ),
            name=u"index")
    )

## SelectRelatedMixin

A simple mixin which allows you to specify a list or tuple of foreign key fields to perform a select_related on. See Django’s docs for more information on select_related.

    # views.py
    from django.views.generic import DetailView

    from braces.views import SelectRelatedMixin

    from profiles.models import Profile

    class UserProfileView(SelectRelatedMixin, DetailView):
        model = Profile
        select_related = [u"user"]
        template_name = u"profiles/detail.html"

## PrefetchRelatedMixin

A simple mixin which allows you to specify a list or tuple of reverse foreign key or ManyToMany fields to perform a prefetch_related on. See Django’s docs for more information on prefetch_related.

    # views.py
    from django.contrib.auth.models import User
    from django.views.generic import DetailView

    from braces.views import PrefetchRelatedMixin

    class UserView(PrefetchRelatedMixin, DetailView):
        model = User
        prefetch_related = [u"post_set"]  # where the Post model has an FK to the User model as an author.
        template_name = u"users/detail.html"

## JSONResponseMixin

Changed in version 1.1: `render_json_response` now accepts a `status` keyword argument. `json_dumps_kwargs` class-attribute and `get_json_dumps_kwargs` method to provide arguments to the `json.dumps()` method.

A simple mixin to handle very simple serialization as a response to the browser.

    # views.py
    from django.views.generic import DetailView

    from braces.views import JSONResponseMixin

    class UserProfileAJAXView(JSONResponseMixin, DetailView):
        model = Profile
        json_dumps_kwargs = {u"indent": 2}

        def get(self, request, *args, **kwargs):
            self.object = self.get_object()

            context_dict = {
                u"name": self.object.user.name,
                u"location": self.object.location
            }

            return self.render_json_response(context_dict)

You can additionally use the AjaxResponseMixin

    # views.py
    from django.views import DetailView

    from braces import views

    class UserProfileView(views.JSONResponseMixin,
                          views.AjaxResponseMixin,
                          DetailView):
        model = Profile

        def get_ajax(self, request, *args, **kwargs):
            return self.render_json_object_response(self.get_object())

The JSONResponseMixin provides a class-level variable to control the response type as well. By default it is application/json, but you can override that by providing the content_type variable a different value or, programmatically, by overriding the get_content_type() method.

    from django.views import DetailView

    from braces.views import JSONResponseMixin

    class UserProfileAJAXView(JSONResponseMixin, DetailView):
        content_type = u"application/javascript"
        model = Profile

        def get(self, request, *args, **kwargs):
            self.object = self.get_object()

            context_dict = {
                u"name": self.object.user.name,
                u"location": self.object.location
            }

            return self.render_json_response(context_dict)

        def get_content_type(self):
            # Shown just for illustrative purposes
            return u"application/javascript"

The JSONResponseMixin provides another class-level variable json_encoder_class to use a custom json encoder with json.dumps. By default it is django.core.serializers.json.DjangoJsonEncoder

    from django.core.serializers.json import DjangoJSONEncoder

    from braces.views import JSONResponseMixin

    class SetJSONEncoder(DjangoJSONEncoder):
        """
        A custom JSONEncoder extending `DjangoJSONEncoder` to handle serialization
        of `set`.
        """
        def default(self, obj):
            if isinstance(obj, set):
                return list(obj)
            return super(DjangoJSONEncoder, self).default(obj)

    class GetSetDataView(JSONResponseMixin, View):
        json_encoder_class = SetJSONEncoder

        def get(self, request, *args, **kwargs):
            numbers_set = set(range(10))
            data = {'numbers': numbers_set}
            return self.render_json_response(data)

## JsonRequestResponseMixin

Added in version 1.3.

A mixin that attempts to parse the request as JSON. If the request is properly formatted, the JSON is saved to `self.request_json` as a Python object. `request_json` will be `None` for imparsible requests.

To catch requests that aren’t JSON-formatted, set the class attribute `require_json` to `True`.

Override the class attribute `error_response_dict` to customize the default error message.

It extends JSONResponseMixin, so those utilities are available as well.

Note

To allow public access to your view, you’ll need to use the `csrf_exempt` decorator or CsrfExemptMixin.

    from django.views.generic import View

    from braces import views

    class SomeView(views.CsrfExemptMixin, views.JsonRequestResponseMixin, View):
        require_json = True

        def post(self, request, *args, **kwargs):
            try:
                burrito = self.request_json[u"burrito"]
                toppings = self.request_json[u"toppings"]
            except KeyError:
                error_dict = {u"message":
                   u"your order must include a burrito AND toppings"}
                return self.render_bad_request_response(error_dict)
            place_order(burrito, toppings)
            return self.render_json_response(
                {u"message": u"Your order has been placed!"})

## AjaxResponseMixin

This mixin provides hooks for alternate processing of AJAX requests based on HTTP verb.

To control AJAX-specific behavior, override `get_ajax`, `post_ajax`, `put_ajax`, or `delete_ajax`. All four methods take `request`, `*args`, and `**kwargs` like the standard view methods.

    # views.py
    from django.views.generic import View

    from braces import views

    class SomeView(views.JSONResponseMixin, views.AjaxResponseMixin, View):
        def get_ajax(self, request, *args, **kwargs):
            json_dict = {
                'name': "Benny's Burritos",
                'location': "New York, NY"
            }
            return self.render_json_response(json_dict)

Note

This mixin is only useful if you need to have behavior in your view fork based on `request.is_ajax()`.

## OrderableListMixin

Added in version 1.1.

A mixin to allow easy ordering of your queryset basing on the GET parameters. Works with ListView.

To use it, define columns that the data can be ordered by, as well as the default column to order by in your view. This can be done either by simply setting the class attributes:

    # views.py
    from django.views import ListView

    from braces.views import OrderableListMixin

    class OrderableListView(OrderableListMixin, ListView):
        model = Article
        orderable_columns = (u"id", u"title",)
        orderable_columns_default = u"id"

Or by using similarly-named methods to set the ordering constraints more dynamically:

    # views.py
    from django.views import ListView

    from braces.views import OrderableListMixin

    class OrderableListView(OrderableListMixin, ListView):
        model = Article

        def get_orderable_columns(self):
            # return an iterable
            return (u"id", u"title",)

        def get_orderable_columns_default(self):
            # return a string
            return u"id"

The `orderable_columns` restriction is here in order to stop your users from launching inefficient queries, like ordering by binary columns.

`OrderableListMixin` will order your queryset basing on following GET params:

> - `order_by`: column name, e.g. `"title"`

> - `ordering`: `"asc"` (default) or `"desc"`

Example url: http://127.0.0.1:8000/articles/?order_by=title&ordering=asc

You can also override the default ordering from `"asc"` to `"desc"` by setting the `"ordering_default"` in your view class.

    # views.py
    from django.views import ListView

    from braces.views import OrderableListMixin

    class OrderableListView(OrderableListMixin, ListView):
        model = Article
        orderable_columns = (u"id", u"title",)
        orderable_columns_default = u"id"
        ordering_default = u"desc"

This will reverse the order of list objects if no query param is given.

Front-end Example Usage

If you’re using bootstrap you could create a template like the following:

    <div class="table-responsive">
        <table class="table table-striped table-bordered">
            <tr>
                <th><a class="order-by-column" data-column="id" href="#">ID</a></th>
                <th><a class="order-by-column" data-column="title" href="#">Title</a></th>
            </tr>
            {% for object in object_list %}
                <tr>
                    <td>{{ object.id }}</td>
                    <td>{{ object.title }}</td>
                </tr>
            {% endfor %}
        </table>
    </div>

    <script>
    function setupOrderedColumns(order_by, orderin) {

        $('.order-by-column').each(function() {

            var $el = $(this),
                column_name = $el.data('column'),
                href = location.href,
                next_order = 'asc',
                has_query_string = (href.indexOf('?') !== -1),
                order_by_param,
                ordering_param;

            if (order_by === column_name) {
                $el.addClass('current');
                $el.addClass(ordering);
                $el.append('<span class="caret"></span>');
                if (ordering === 'asc') {
                    $el.addClass('dropup');
                    next_order = 'desc';
                }
            }

            order_by_param = "order_by=" + column_name;
            ordering_param = "ordering=" + next_order;

            if (!has_query_string) {
                href = '?' + order_by_param + '&' + ordering_param;
            } else {
                if (href.match(/ordering=(asc|desc)/)) {
                    href = href.replace(/ordering=(asc|desc)/, ordering_param);
                } else {
                    href += '&' + ordering_param;
                }

                if (href.match(/order_by=[_\w]+/)) {
                    href = href.replace(/order_by=([_\w]+)/, order_by_param);
                } else {
                    href += '&' + order_by_param;
                }

            }

            $el.attr('href', href);

        });
    }
    setupOrderedColumns('{{ order_by }}', '{{ ordering }}');
    </script>

## CanonicalSlugDetailMixin

Added in version 1.3.

A mixin that enforces a canonical slug in the URL. Works with `DetailView`.

If a `urlpattern` takes a object’s `pk` and `slug` as arguments and the `slug` URL argument does not equal the object’s canonical slug, this mixin will redirect to the URL containing the canonical slug.

To use it, the `urlpattern` must accept both a `pk` and `slug` argument in its regex:

    # urls.py
    urlpatterns = patterns('',
        url(r"^article/(?P<pk>\d+)-(?P<slug>[-\w]+)$")
        ArticleView.as_view(),
        "view_article"
    )

Then create a standard `DetailView` that inherits this mixin:

    class ArticleView(CanonicalSlugDetailMixin, DetailView):
        model = Article

Now, given an `Article` object with `{pk: 1, slug: 'hello-world'}`, the URL http://127.0.0.1:8000/article/1-goodbye-moon will redirect to http://127.0.0.1:8000/article/1-hello-world with the HTTP status code 301 Moved Permanently. Any other non-canonical slug, not just ‘goodbye-moon’, will trigger the redirect as well.

Control the canonical slug by either implementing the method `get_canonical_slug()` on the model class:

    class Article(models.Model):
        blog = models.ForeignKey('Blog')
        slug = models.SlugField()

        def get_canonical_slug(self):
          return "{0}-{1}".format(self.blog.get_canonical_slug(), self.slug)

Or by overriding the `get_canonical_slug()` method on the view:

    class ArticleView(CanonicalSlugDetailMixin, DetailView):
        model = Article

        def get_canonical_slug():
            import codecs
            return codecs.encode(self.get_object().slug, "rot_13")

Given the same Article as before, this will generate urls of http://127.0.0.1:8000/article/1-my-blog-hello-world and http://127.0.0.1:8000/article/1-uryyb-jbeyq, respectively.

## MessageMixin

Added in version 1.4.

A mixin that adds a `messages` attribute on the view which acts as a wrapper to `django.contrib.messages` and passes the `request` object automatically.

> Warning

> If you’re using Django 1.4, then the `message` attribute is only available after the base view’s `dispatch` method has been called (so our second example would not work for instance).

    from django.views.generic import TemplateView

    from braces.views import MessageMixin

    class MyView(MessageMixin, TemplateView):
        """
        This view will add a debug message which can then be displayed
        in the template.
        """
        template_name = "my_template.html"

        def get(self, request, *args, **kwargs):
            self.messages.debug("This is a debug message.")
            return super(MyView, self).get(request, *args, **kwargs)

    from django.contrib import messages
    from django.views.generic import TemplateView

    from braces.views import MessageMixin

    class OnlyWarningView(MessageMixin, TemplateView):
        """
        This view will only show messages that have a level
        above `warning`.
        """
        template_name = "my_template.html"

        def dispatch(self, request, *args, **kwargs):
            self.messages.set_level(messages.WARNING)
            return super(OnlyWarningView, self).dispatch(request, *args, **kwargs)

## AllVerbsMixin

Added in version 1.4.

This mixin allows you to specify a single method that will respond to all HTTP verbs, making a class-based view behave much like a function-based view.

    from django.views import TemplateView

    from braces.views import AllVerbsMixin

    class JustShowItView(AllVerbsMixin, TemplateView):
        template_name = "just/show_it.html"

        def all(self, request, *args, **kwargs):
            return super(JustShowItView, self).get(request, *args, **kwargs)

If you need to change the name of the method called, provide a new value to the `all_handler` attribute (default is `'all'`)

## HeaderMixin

Added in version 1.11.

This mixin allows you to add arbitrary HTTP header to a response. Static headers can be defined in the `headers` attribute of the view.

    from django.views import TemplateView

    from braces.views import HeaderMixin

    class StaticHeadersView(HeaderMixin, TemplateView):
        template_name = "some/headers.html"
        headers = {
            'X-Header-Sample': 'some value',
            'X-Some-Number': 42
        }

If you need to set the headers dynamically, e.g depending on some request information, override the `get_headers` method instead.

    from django.views import TemplateView

    from braces.views import HeaderMixin

    class EchoHeadersView(HeaderMixin, TemplateView):
        template_name = "some/headers.html"

        def get_headers(self, request):
            """
            Echo back request headers with ``X-Request-`` prefix.
            """
            for key, value in request.META.items():
                yield "X-Request-{}".format(key), value

## CacheControlMixin

Mixin that allows setting `Cache-Control` header options.

`Cache-Control` directive explanations:

http://condor.depaul.edu/dmumaugh/readings/handouts/SE435/HTTP/node24.html

Django’s `django.views.decorators.cache.cache_control` options:

https://docs.djangoproject.com/en/dev/topics/cache/#controlling-cache-using-other-headers

    from django.views import TemplateView
    from braces.views import CacheControlMixin

    class MyView(CacheControlMixin, TemplateView):
        template_name = "project/template.html"

        # Specify Cache-Control options as class-level attributes.
        # The arguments are passed to Django's `cache_control()` view decorator
        # directly (with the `cachecontrol_` prefix removed.)
        cachecontrol_public = True
        cachecontrol_max_age = 60

        # Alternatively, you can implement the ``get_cachecontrol_options()``
        # classmethod that should return a dictionary of the kwargs passed to
        # Django's `cache_control()` view decorator.
        @classmethod
        def get_cachecontrol_options(cls):
            return {'public': True, 'max_age': 60}

This will cause the following header to be emitted for every request to this view:

    Cache-Control: public, max-age=60

Available `Cache-Control` options:

    # These are all `None` by default, which indicates unset.
    cachecontrol_public = None
    cachecontrol_private = None
    cachecontrol_no_cache = None
    cachecontrol_no_transform = None
    cachecontrol_must_revalidate = None
    cachecontrol_proxy_revalidate = None
    cachecontrol_max_age = None
    cachecontrol_s_maxage = None

## NeverCacheMixin

Mixin that applies Django’s `django.views.decorators.cache.never_cache` view decorator to prevent upstream HTTP-based caching.

    from django.views import TemplateView
    from braces.views import NeverCacheMixin

    class MyView(NeverCacheMixin, TemplateView):
        template_name = "project/template.html"

This will cause the following header to be emitted for every request to this view:

    Cache-Control: max-age=0, no-cache, no-store, must-revalidate