Extending the page & title models

New in version 3.0.

You can extend the page and title models with your own fields (e.g. adding an icon for every page) by using the extension models: cms.extensions.PageExtension and cms.extensions.TitleExtension, respectively.

What’s the difference?

The difference between a page extension and a title extension is related to the difference between the Page and Title models. Titles support pages by providing a storage mechanism, amoung other things, for language-specific properties of Pages. So, if you find that you need to extend the page model in a language-specific manner, for example, if you need to create language- specific keywords for each language of your pages, then you may need to use a TitleExtension. If the extension you’d like to create is the same for all of the different languages of the page, then you may be fine using a PageExtension.

How To

To add a field to the page model, create a class that inherits from cms.extensions.PageExtension. Make sure to import the cms.extensions.PageExtension model. Your class should live in one of your apps’ models.py (or module). Since PageExtension (and TitleExtension) inherit from django.db.models.Model, you are free to add any field you want but make sure you don’t use a unique constraint on any of your added fields because uniqueness prevents the copy mechanism of the extension from working correctly. This means that you can’t use one-to-one relations on the extension model. Finally, you’ll need to register the model with using extension_pool.

Here’s a simple example which adds an icon field to the page:

from django.db import models

from cms.extensions import PageExtension
from cms.extensions.extension_pool import extension_pool

class IconExtension(PageExtension):
    image = models.ImageField(upload_to='icons')


Hooking the extension to the admin site

To make your extension editable, you must first create an admin class that subclasses cms.extensions.PageExtensionAdmin. This admin handles page permissions. If you want to use your own admin class, make sure to exclude the live versions of the extensions by using filter(extended_page__publisher_is_draft=True) on the queryset.

Continuing with the example model above, here’s a simple corresponding PageExtensionAdmin class:

from django.contrib import admin
from cms.extensions import PageExtensionAdmin

from .models import IconExtension

class IconExtensionAdmin(PageExtensionAdmin):

admin.site.register(IconExtension, IconExtensionAdmin)

Since PageExtensionAdmin inherits from ModelAdmin, you’ll be able to use the normal set of Django ModelAdmin properties, as appropriate to your circumstance.

Once you’ve registered your admin class, a new model will appear in the top- level admin list.

Note that the field that holds the relationship between the extension and a CMS Page is non-editable, so it will not appear in the admin views. This, unfortunately, leaves the operator without a means of “attaching” the page extension to the correct pages. The way to address this is to use a CMSToolbar. Note that creating the admin hook is still required, because it creates the add and change admin forms that are required for the next step.

Adding a Toolbar Menu Item for your Page extension

You’ll also want to make your model editable from the cms toolbar in order to associate each instance of the extension model with a page. (Page isn’t an editable attribute in the default admin interface.) The following example, which should live in a file named cms_toolbar.py in one of your apps, adds a menu entry for the extension on each page:

from cms.api import get_page_draft
from cms.toolbar_pool import toolbar_pool
from cms.toolbar_base import CMSToolbar
from cms.utils import get_cms_setting
from cms.utils.permissions import has_page_change_permission
from django.core.urlresolvers import reverse, NoReverseMatch
from django.utils.translation import ugettext_lazy as _
from .models import IconExtension

class IconExtensionToolbar(CMSToolbar):
    def populate(self):
        # always use draft if we have a page
        self.page = get_page_draft(self.request.current_page)

        if not self.page:
            # Nothing to do

        # check global permissions if CMS_PERMISSIONS is active
        if get_cms_setting('PERMISSION'):
            has_global_current_page_change_permission = has_page_change_permission(self.request)
            has_global_current_page_change_permission = False
            # check if user has page edit permission
        can_change = self.request.current_page and self.request.current_page.has_change_permission(self.request)
        if has_global_current_page_change_permission or can_change:
                icon_extension = IconExtension.objects.get(extended_object_id=self.page.id)
            except IconExtension.DoesNotExist:
                icon_extension = None
                if icon_extension:
                    url = reverse('admin:myapp_iconextension_change', args=(icon_extension.pk,))
                    url = reverse('admin:myapp_iconextension_add') + '?extended_object=%s' % self.page.pk
            except NoReverseMatch:
                # not in urls
                not_edit_mode = not self.toolbar.edit_mode
                current_page_menu = self.toolbar.get_or_create_menu('page')
                current_page_menu.add_modal_item(_('Page Icon'), url=url, disabled=not_edit_mode)

Now when the operator invokes “Edit this page...” from the toolbar, there will be an additional menu item Page Icon ... (in this case), which can be used to open a modal dialog where the operator can affect the new icon field.

Note that when the extension is saved, the corresponding page is marked as having unpublished changes. To see the new extension values make sure to publish the page.

Using extensions with menus

If you want the extension to show up in the menu (e.g. if you had created an extension that added an icon to the page) use menu modifiers. Every node.id corresponds to their related page.id. Page.objects.get(pk=node.id) is the way to get the page object. Every page extension has a one-to-one relationship with the page so you can access it by using the reverse relation, e.g. extension = page.yourextensionlowercased. Now you can hook this extension by storing it on the node: node.extension = extension. In the menu template you can access your icon on the child object: child.extension.icon.

Using extensions in templates

To access a page extension in page templates you can simply access the approriate related_name field that is now available on the Page object.

As per the normal related_name naming mechanism, the appropriate field to access is the same as your PageExtension model name, but lowercased. Assuming your Page Extension model class is IconExtension, the relationship to the page extension model will be available on page.iconextension. From there you can access the extra fields you defined in your extension, so you can use something like:

{% load staticfiles %}

{# rest of template omitted ... #}

{% if request.current_page.iconextension %}
    <img src="{% static request.current_page.iconextension.image.url %}">
{% endif %}

Where request.current_page is the normal way to access the current page that is rendering the template.

It is important to remember that unless the operator has already assigned a page extension to every page, a page may not have the iconextension relationship available, hence the use of the {% if ... %}...{% endif %} above.

Handling relations

If your PageExtension or TitleExtension includes a ForeignKey from another model or includes a ManyToMany field, you should also override the method copy_relations(self, oldinstance, language) so that these fields are copied appropriately when the CMS makes a copy of your extension to support versioning, etc.

Here’s an example that uses a ManyToMany` field:

from django.db import models
from cms.extensions import PageExtension
from cms.extensions.extension_pool import extension_pool

class MyPageExtension(PageExtension):

    page_categories = models.ManyToMany('categories.Category', blank=True, null=True)

    def copy_relations(self, oldinstance, language):
        for page_category in oldinstance.page_categories.all():
            page_category.pk = None
            page_category.mypageextension = self