Question

I have a Competition model which has a corresponding CompetitionEntry model. I’d like to show the number of entries for each competition in the admin view.

Here’s the model definition:

class Competition(models.Model):

    def __unicode__(self):
        return self.competition_name

    competition_name = models.CharField(max_length=100)
    competition_text = models.TextField()
    active = models.BooleanField('Is this competition active?', blank=True)
    date_posted = models.DateTimeField(auto_now_add=True)

class CompetitionEntry(models.Model):

    def __unicode__(self):
        return self.competition.competition_name

    competition = models.ForeignKey(Competition)
    user = models.ForeignKey(User)
    date_entered = models.DateTimeField(auto_now_add=True)
    is_winner = models.BooleanField('Is this entry the winner?', blank=True)

My Django skills are a little rusty, but there should be a fairly simple way to add this to the admin, right? Any pointers? I can’t quite work out how the Competition class can ‘talk’ to the CompetitionEntry class since the relationship is defined inside CompetitionEntry, but I want to show the entries inside Competition.

Answer 1

You can refer to python functions in a ModelAdmin by adding it to the fieldsets or list_display and readonly_fields attributes.

You can ‘talk’ to a reverse relationship via the reverse related managers dynamically added to each class that a foreign key points to which is, by default, lowercasemodelname_set and behaves exactly like your default objects manager.

class MyAdmin(admin.ModelAdmin):
    list_display = ('_competition_count',)
    readonly_fields = ('_competition_count',)

    fieldsets = (
        (None, {'fields': (
            '_competition_count',
        )})
    )

    def _competition_count(self, obj):
        return obj.competitionentry_set.count()
    _competition_count.short_description = "Competition Count"