使用django中的另一个模型在模型中求和金额字段

Question

I have three models: User, Campaign and Donation. The donation model has a donation amount, donated by each user against each campaign.

Campaign model

class Campaign(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    # this is many to one relationship, on_deleting user, profile will also be deleted
    campaign_title = models.CharField(max_length=200, blank=True)

Donation model

class Donation(models.Model):
    user = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
    # this is many to one relationship, on_deleting user, user's donation details will be set to NULL
    campaign = models.ForeignKey(Campaign, on_delete=models.DO_NOTHING)
    donation_amount = models.IntegerField()

views.py file

def landing_page(request):
    # campaigns = Campaign.objects.all().order_by('-id')
    campaigns = Campaign.objects.all().order_by('-id')

    ////DO SOMETHING HERE TO SHOW TOTAL DONATION AGAINST EACH CAMPAIGN////

    return render(request, 'core/landing_page.html',{'campaigns':campaigns})

Using the current views.py file, I'm able to display all the campaigns, how do I pass the total donation against each campaign to the html file?

Answer 1

You can use annotate like this.

from django.db.models import Sum

campaigns = Campaign.objects.annotate(donations=Sum('donation__donation_amount'))

Every compaign object will have a donations attribute with value to sum of total donations for that compaign.