===========
Page models
===========

Each page type (a.k.a. content type) in Wagtail is represented by a Django model. All page models must inherit from the :class:`wagtail.wagtailcore.models.Page` class.

As all page types are Django models, you can use any field type that Django provides. See `Model field reference <https://docs.djangoproject.com/en/1.9/ref/models/fields/>`_ for a complete list of field types you can use. Wagtail also provides :class:`~wagtail.wagtailcore.fields.RichTextField` which provides a WYSIWYG editor for editing rich-text content.


.. topic:: Django models

    If you're not yet familiar with Django models, have a quick look at the following links to get you started:

    * `Creating models <https://docs.djangoproject.com/en/1.9/intro/tutorial02/#creating-models>`_
    * `Model syntax <https://docs.djangoproject.com/en/1.9/topics/db/models/>`_


An example Wagtail page model
=============================

This example represents a typical blog post:

.. code-block:: python

    from django.db import models

    from modelcluster.fields import ParentalKey

    from wagtail.wagtailcore.models import Page, Orderable
    from wagtail.wagtailcore.fields import RichTextField
    from wagtail.wagtailadmin.edit_handlers import FieldPanel, MultiFieldPanel, InlinePanel
    from wagtail.wagtailimages.edit_handlers import ImageChooserPanel
    from wagtail.wagtailsearch import index


    class BlogPage(Page):

        # Database fields

        body = RichTextField()
        date = models.DateField("Post date")
        feed_image = models.ForeignKey(
            'wagtailimages.Image',
            null=True,
            blank=True,
            on_delete=models.SET_NULL,
            related_name='+'
        )


        # Search index configuration

        search_fields = Page.search_fields + [
            index.SearchField('body'),
            index.FilterField('date'),
        ]


        # Editor panels configuration

        content_panels = Page.content_panels + [
            FieldPanel('date'),
            FieldPanel('body', classname="full"),
            InlinePanel('related_links', label="Related links"),
        ]

        promote_panels = [
            MultiFieldPanel(Page.promote_panels, "Common page configuration"),
            ImageChooserPanel('feed_image'),
        ]


        # Parent page / subpage type rules

        parent_page_types = ['blog.BlogIndex']
        subpage_types = []


    class BlogPageRelatedLink(Orderable):
        page = ParentalKey(BlogPage, related_name='related_links')
        name = models.CharField(max_length=255)
        url = models.URLField()

        panels = [
            FieldPanel('name'),
            FieldPanel('url'),
        ]

.. important::

    Ensure that none of your field names are the same as your class names. This will cause errors due to the way Django handles relations (`read more <https://github.com/torchbox/wagtail/issues/503>`_). In our examples we have avoided this by appending "Page" to each model name.


Writing page models
===================

Here we'll describe each section of the above example to help you create your own page models.


Database fields
---------------

Each Wagtail page type is a Django model, represented in the database as a separate table.

Each page type can have its own set of fields. For example, a news article may have body text and a published date, whereas an event page may need separate fields for venue and start/finish times.

In Wagtail, you can use any Django field class. Most field classes provided by `third party apps <https://code.djangoproject.com/wiki/DjangoResources#Djangoapplicationcomponents>`_ should work as well.

Wagtail also provides a couple of field classes of its own:

 - ``RichTextField`` - For rich text content
 - ``StreamField`` - A block-based content field (see: :doc:`/topics/streamfield`)

For tagging, Wagtail fully supports `django-taggit <https://django-taggit.readthedocs.org/en/latest/>`_ so we recommend using that.


Search
------

The ``search_fields`` attribute defines which fields are added to the search index and how they are indexed.

This should be a list of ``SearchField`` and ``FilterField`` objects. ``SearchField`` adds a field for full-text search. ``FilterField`` adds a field for filtering the results. A field can be indexed with both ``SearchField`` and ``FilterField`` at the same time (but only one instance of each).

In the above example, we've indexed ``body`` for full-text search and ``date`` for filtering.

The arguments that these field types accept are documented in :ref:`wagtailsearch_indexing_fields`.


Editor panels
-------------

There are a few attributes for defining how the page's fields will be arranged in the page editor interface:

 - ``content_panels`` - For content, such as main body text
 - ``promote_panels`` - For metadata, such as tags, thumbnail image and SEO title
 - ``settings_panels`` - For settings, such as publish date

Each of these attributes is set to a list of ``EditHandler`` objects, which defines which fields appear on which tabs and how they are structured on each tab.

Here's a summary of the ``EditHandler`` classes that Wagtail provides out of the box. See :doc:`/reference/pages/panels` for full descriptions.

**Basic**

These allow editing of model fields. The ``FieldPanel`` class will choose the correct widget based on the type of the field, though ``StreamField`` fields need to use a specialised panel class.

 - :class:`~wagtail.wagtailadmin.edit_handlers.FieldPanel`
 - :class:`~wagtail.wagtailadmin.edit_handlers.StreamFieldPanel`

**Structural**

These are used for structuring fields in the interface.

 - :class:`~wagtail.wagtailadmin.edit_handlers.MultiFieldPanel` - For grouping similar fields together
 - :class:`~wagtail.wagtailadmin.edit_handlers.InlinePanel` - For inlining child models
 - :class:`~wagtail.wagtailadmin.edit_handlers.FieldRowPanel` - For organising multiple fields into a single row

**Chooser**

``ForeignKey`` fields to certain models can use one of the below ``ChooserPanel`` classes. These add a nice modal chooser interface, and the image/document choosers also allow uploading new files without leaving the page editor.

 - :class:`~wagtail.wagtailadmin.edit_handlers.PageChooserPanel`
 - :class:`~wagtail.wagtailimages.edit_handlers.ImageChooserPanel`
 - :class:`~wagtail.wagtaildocs.edit_handlers.DocumentChooserPanel`
 - :class:`~wagtail.wagtailsnippets.edit_handlers.SnippetChooserPanel`

.. note::

    In order to use one of these choosers, the model being linked to must either be a page, image, document or snippet.

    To link to any other model type, you should use ``FieldPanel``, which will create a dropdown box.


Customising the page editor interface
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The page editor can be customised further. See :doc:`/advanced_topics/customisation/page_editing_interface`.


.. _page_type_business_rules:

Parent page / subpage type rules
--------------------------------

These two attributes allow you to control where page types may be used in your site. It allows you to define rules like "blog entries may only be created under a blog index".

Both take a list of model classes or model names. Model names are of the format ``app_label.ModelName``. If the ``app_label`` is omitted, the same app is assumed.

- ``parent_page_types`` limits which page types this type can be created under
- ``subpage_types`` limits which page types can be created under this type

By default, any page type can be created under any page type and it is not necessary to set these attributes if that's the desired behaviour.

Setting ``parent_page_types`` to an empty list is a good way of preventing a particular page type from being created in the editor interface.


Template rendering
==================

Each page model can be given an HTML template which is rendered when a user browses to a page on the site frontend. This is the simplest and most common way to get Wagtail content to end users (but not the only way).


Adding a template for a page model
----------------------------------

Wagtail automatically chooses a name for the template based on the app label and model class name.

Format: ``<app_label>/<model_name (snake cased)>.html``

For example, the template for the above blog page will be: ``blog/blog_page.html``

You just need to create a template in a location where it can be accessed with this name.


Template context
----------------

Wagtail renders templates with the ``page`` variable bound to the page instance being rendered. Use this to access the content of the page. For example, to get the title of the current page, use ``{{ page.title }}``. All variables provided by `context processors <https://docs.djangoproject.com/en/1.8/ref/templates/api/#subclassing-context-requestcontext>`_ are also available.


Customising template context
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

All pages have a ``get_context`` method that is called whenever the template is rendered and returns a dictionary of variables to bind into the template.

To add more variables to the template context, you can override this method:

.. code-block:: python

    class BlogIndexPage(Page):
        ...

        def get_context(self, request):
            context = super(BlogIndexPage, self).get_context(request)

            # Add extra variables and return the updated context
            context['blog_entries'] = BlogPage.objects.child_of(self).live()
            return context


The variables can then be used in the template:

.. code-block:: HTML+Django

    {{ page.title }}

    {% for entry in blog_entries %}
        {{ entry.title }}
    {% endfor %}


Changing the template
---------------------

Set the ``template`` attribute on the class to use a different template file:

.. code-block:: python

    class BlogPage(Page):
        ...

        template = 'other_template.html'


Dynamically choosing the template
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The template can be changed on a per-instance basis by defining a ``get_template`` method on the page class. This method is called every time the page is rendered:

.. code-block:: python

    class BlogPage(Page):
        ...

        use_other_template = models.BooleanField()

        def get_template(self, request):
            if self.use_other_template:
                return 'blog/other_blog_page.html'

            return 'blog/blog_page.html'

In this example, pages that have the ``use_other_template`` boolean field set will use the ``blog/other_blog_page.html`` template. All other pages will use the default ``blog/blog_page.html``.


More control over page rendering
--------------------------------

All page classes have a ``serve()`` method that internally calls the ``get_context`` and ``get_template`` methods and renders the template. This method is similar to a Django view function, taking a Django ``Request`` object and returning a Django ``Response`` object.

This method can also be overridden for complete control over page rendering.

For example, here's a way to make a page respond with a JSON representation of itself:

.. code-block:: python

    from django.http import JsonResponse


    class BlogPage(Page):
        ...

        def serve(self, request):
            return JsonResponse({
                'title': self.title,
                'body': self.body,
                'date': self.date,

                # Resizes the image to 300px width and gets a URL to it
                'feed_image': self.feed_image.get_rendition('width-300').url,
            })


Inline models
=============

Wagtail can nest the content of other models within the page. This is useful for creating repeated fields, such as related links or items to display in a carousel. Inline model content is also versioned with the rest of the page content.

Each inline model requires the following:

 - It must inherit from :class:`wagtail.wagtailcore.models.Orderable`
 - It must have a ``ParentalKey`` to the parent model

.. note:: django-modelcluster and ParentalKey

    The model inlining feature is provided by `django-modelcluster <https://github.com/torchbox/django-modelcluster>`_ and the ``ParentalKey`` field type must be imported from there:

    .. code-block:: python

        from modelcluster.fields import ParentalKey

    ``ParentalKey`` is a subclass of Django's ``ForeignKey``, and takes the same arguments.


For example, the following inline model can be used to add related links (a list of name, url pairs) to the ``BlogPage`` model:

.. code-block:: python

    from django.db import models
    from modelcluster.fields import ParentalKey
    from wagtail.wagtailcore.models import Orderable


    class BlogPageRelatedLink(Orderable):
        page = ParentalKey(BlogPage, related_name='related_links')
        name = models.CharField(max_length=255)
        url = models.URLField()

        panels = [
            FieldPanel('name'),
            FieldPanel('url'),
        ]

To add this to the admin interface, use the :class:`~wagtail.wagtailadmin.edit_handlers.InlinePanel` edit panel class:

.. code-block:: python

    content_panels = [
        ...

        InlinePanel('related_links', label="Related links"),
    ]

The first argument must match the value of the ``related_name`` attribute of the ``ParentalKey``.


Working with pages
==================

Wagtail uses Django's `multi-table inheritance <https://docs.djangoproject.com/en/1.8/topics/db/models/#multi-table-inheritance>`_ feature to allow multiple page models to be used in the same tree.

Each page is added to both Wagtail's builtin :class:`~wagtail.wagtailcore.models.Page` model as well as its user-defined model (such as the ``BlogPage`` model created earlier).

Pages can exist in Python code in two forms, an instance of ``Page`` or an instance of the page model.

 When working with multiple page types together, you will typically use instances of Wagtail's :class:`~wagtail.wagtailcore.models.Page` model, which don't give you access to any fields specific to their type.

.. code-block:: python

    # Get all pages in the database
    >>> from wagtail.wagtailcore.models import Page
    >>> Page.objects.all()
    [<Page: Homepage>, <Page: About us>, <Page: Blog>, <Page: A Blog post>, <Page: Another Blog post>]

When working with a single page type, you can work with instances of the user-defined model. These give access to all the fields available in ``Page``, along with any user-defined fields for that type.

.. code-block:: python

    # Get all blog entries in the database
    >>> BlogPage.objects.all()
    [<BlogPage: A Blog post>, <BlogPage: Another Blog post>]

You can convert a ``Page`` object to its more specific user-defined equivalent using the ``.specific`` property. This may cause an additional database lookup.

.. code-block:: python

    >>> page = Page.objects.get(title="A Blog post")
    >>> page
    <Page: A Blog post>

    # Note: the blog post is an instance of Page so we cannot access body, date or feed_image

    >>> page.specific
    <BlogPage: A Blog post>


Tips
====

Friendly model names
--------------------

You can make your model names more friendly to users of Wagtail by using Django's internal ``Meta`` class with a ``verbose_name``, e.g.:

.. code-block:: python

    class HomePage(Page):
        ...

        class Meta:
            verbose_name = "homepage"

When users are given a choice of pages to create, the list of page types is generated by splitting your model names on each of their capital letters. Thus a ``HomePage`` model would be named "Home Page" which is a little clumsy. Defining ``verbose_name`` as in the example above would change this to read "Homepage", which is slightly more conventional.


Page QuerySet ordering
----------------------

``Page``-derived models *cannot* be given a default ordering by using the standard Django approach of adding an ``ordering`` attribute to the internal ``Meta`` class.

.. code-block:: python

    class NewsItemPage(Page):
        publication_date = models.DateField()
        ...

        class Meta:
            ordering = ('-publication_date', )  # will not work

This is because ``Page`` enforces ordering QuerySets by path. Instead, you must apply the ordering explicitly when constructing a QuerySet:

.. code-block:: python

    news_items = NewsItemPage.objects.live().order_by('-publication_date')

.. _custom_page_managers:

Custom Page managers
--------------------

You can add a custom ``Manager`` to your ``Page`` class. Any custom Managers should inherit from :class:`wagtail.wagtailcore.models.PageManager`:

.. code-block:: python

    from django.db import models
    from wagtail.wagtailcore.models import Page, PageManager

    class EventPageManager(PageManager):
        """ Custom manager for Event pages """

    class EventPage(Page):
        start_date = models.DateField()

        objects = EventPageManager()

Alternately, if you only need to add extra ``QuerySet`` methods, you can inherit from :class:`wagtail.wagtailcore.models.PageQuerySet`, and call :func:`~django.db.models.managers.Manager.from_queryset` to build a custom ``Manager``:

.. code-block:: python

    from django.db import models
    from django.utils import timezone
    from wagtail.wagtailcore.models import Page, PageManager, PageQuerySet

    class EventPageQuerySet(PageQuerySet):
        def future(self):
            today = timezone.localtime(timezone.now()).date()
            return self.filter(start_date__gte=today)

    EventPageManager = PageManager.from_queryset(EventPageQuerySet)

    class EventPage(Page):
        start_date = models.DateField()

        objects = EventPageManager()
