wagtail_bakerydemo/bakerydemo/breads/models.py

from django import forms
from django.db import models
from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger

from modelcluster.fields import ParentalManyToManyField

from wagtail.wagtailadmin.edit_handlers import FieldPanel, MultiFieldPanel
from wagtail.wagtailcore.models import Page
from wagtail.wagtailsearch import index
from wagtail.wagtailsnippets.models import register_snippet
from wagtail.wagtailimages.edit_handlers import ImageChooserPanel

from bakerydemo.base.models import BasePageFieldsMixin


@register_snippet
class Country(models.Model):
    """
    A Django model to store set of countries of origin.
    It uses the `@register_snippet` decorator to allow it to be accessible
    via the Snippets UI (e.g. /admin/snippets/breads/country/) In the BreadPage
    model you'll see we use a ForeignKey to create the relationship between
    Country and BreadPage. This allows a single relationship (e.g only one
    Country can be added) that is one-way (e.g. Country will have no way to
    access related BreadPage objects).
    """

    title = models.CharField(max_length=100)

    def __str__(self):
        return self.title

    class Meta:
        verbose_name_plural = "Countries of Origin"


@register_snippet
class BreadIngredient(models.Model):
    """
    Standard Django model that is displayed as a snippet within the admin due
    to the `@register_snippet` decorator. We use a new piece of functionality
    available to Wagtail called the ParentalManyToManyField on the BreadPage
    model to display this. The Wagtail Docs give a slightly more detailed example
    http://docs.wagtail.io/en/v1.9/getting_started/tutorial.html#categories
    """
    name = models.CharField(max_length=255)

    panels = [
        FieldPanel('name'),
    ]

    def __str__(self):
        return self.name

    class Meta:
        verbose_name_plural = 'Bread ingredients'


@register_snippet
class BreadType(models.Model):
    """
    A Django model to define the bread type
    It uses the `@register_snippet` decorator to allow it to be accessible
    via the Snippets UI. In the BreadPage model you'll see we use a ForeignKey
    to create the relationship between BreadType and BreadPage. This allows a
    single relationship (e.g only one BreadType can be added) that is one-way
    (e.g. BreadType will have no way to access related BreadPage objects)
    """

    title = models.CharField(max_length=255)

    panels = [
        FieldPanel('title'),
    ]

    def __str__(self):
        return self.title

    class Meta:
        verbose_name_plural = "Bread types"


class BreadPage(BasePageFieldsMixin, Page):
    """
    Detail view for a specific bread
    """

    origin = models.ForeignKey(
        Country,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
    )

    # We include related_name='+' to avoid name collisions on relationships. 
    # e.g. there are two FooPage models in two different apps, 
    # and they both have a FK to bread_type, they'll both try to create a 
    # relationship called `foopage_objects` that will throw a valueError on
    # collision.
    bread_type = models.ForeignKey(
        'breads.BreadType',
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name='+'
    )
    ingredients = ParentalManyToManyField('BreadIngredient', blank=True)

    content_panels = BasePageFieldsMixin.content_panels + [
        FieldPanel('origin'),
        FieldPanel('bread_type'),
        MultiFieldPanel(
            [
                FieldPanel(
                    'ingredients',
                    widget=forms.CheckboxSelectMultiple,
                ),
            ],
            heading="Additional Metadata",
            classname="collapsible collapsed"
        ),
    ]

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

    parent_page_types = ['BreadsIndexPage']


class BreadsIndexPage(BasePageFieldsMixin, Page):
    """
    Index page for breads.

    This is more complex than other index pages on the bakery demo site as we've
    included pagination. We've separated the different aspects of the index page
    to be discrete functions to make it easier to follow
    """

    # Can only have BreadPage children
    subpage_types = ['BreadPage']

    # Returns a queryset of BreadPage objects that are live, that are direct
    # descendants of this index page with most recent first
    def get_breads(self):
        return BreadPage.objects.live().descendant_of(
            self).order_by('-first_published_at')

    # Allows child objects (e.g. BreadPage objects) to be accessible via the
    # template. We use this on the HomePage to display child items of featured
    # content
    def children(self):
        return self.get_children().specific().live()

    # Pagination for the index page. We use the `django.core.paginator` as any
    # standard Django app would, but the difference here being we have it as a
    # method on the model rather than within a view function
    def paginate(self, request, *args):
        page = request.GET.get('page')
        paginator = Paginator(self.get_breads(), 12)
        try:
            pages = paginator.page(page)
        except PageNotAnInteger:
            pages = paginator.page(1)
        except EmptyPage:
            pages = paginator.page(paginator.num_pages)
        return pages

    # Returns the above to the get_context method that is used to populate the
    # template
    def get_context(self, request):
        context = super(BreadsIndexPage, self).get_context(request)

        # BreadPage objects (get_breads) are passed through pagination
        breads = self.paginate(request, self.get_breads())

        context['breads'] = breads

        return context

    content_panels = Page.content_panels + [
        FieldPanel('introduction', classname="full"),
        ImageChooserPanel('image'),
    ]