Ytukyg

Using Wagtail I have ArticlePages, each of which can have 0 or more Authors, which are Snippets.

I'd like to get a list of Authors with the number of ArticlePages they're attached to, but can't work out how. I'm getting confused by ModelCluster I think, as I'd be fine with vanilla Django.

(I'm not even sure if I'm over-complicating this; I don't need the Authors to be orderable on the Articles...)

from django.db import models

from modelcluster.fields import ParentalKey

from wagtail.admin.edit_handlers import InlinePanel

from wagtail.core.models import Orderable, Page

from wagtail.snippets.edit_handlers import SnippetChooserPanel

from wagtail.snippets.models import register_snippet



class ArticlePage(Page):

    content_panels = Page.content_panels + [

        InlinePanel('authors', label='Authors'),

    ]



@register_snippet

class Author(models.Model):

    name = models.CharField(max_length=255, blank=False)



    panels = [

        FieldPanel('name'),

    ]



class ArticleAuthorRelationship(Orderable, models.Model):

    author = models.ForeignKey(

                'Author',

                on_delete=models.CASCADE,

                related_name='+')



    page = ParentalKey(

                'ArticlePage',

                on_delete=models.CASCADE,

                related_name='authors')



    panels = [

        SnippetChooserPanel('author'),

    ]

FWIW, I know I could get a single Author's articles using article.get_usage(), which is handy!

Coming back to this a day later, I think the only issue is having set related_name on ArticleAuthorRelationship's author property to '+' (which means there's no backwards relationship from Author to this model).

If I instead do:

class ArticleAuthorRelationship(Orderable, models.Model):

    author = models.ForeignKey(

                'Author',

                on_delete=models.CASCADE,

                related_name='articles')  # Changed this to 'articles'

    # etc.

Then I can do this quite easily:

from django.db.models import Count

from my app.models import Author



authors = Author.objects.annotate(num_articles=Count('articles')).order_by('-num_articles')

Then each item in the authors QuerySet has a num_articles property.

I usually set a related_name but this seems less common in the Wagtail docs, and I almost hadn't noticed I'd copied that behaviour here, so this threw me.

If anyone's reading this and can give examples of why/when you'd want to set related_name to '+', I'd be interested to know. Thanks.