How to create relationships between 3 models in django?

I’m building a marketplace that have 2 user types i.e. buyers and sellers.

Now I want to create a relationship model between buyers, sellers and OrderedItems, so that the sellers gets notified once the buyers orders an item.

This is the model I made:

class Ordered(models.Model):
    ordered_items = models.ManyToManyField(Cart)
    seller = models.ForeignKey(SellerProfile, on_delete = models.SET_NULL, null = True)
    buyer = models.ForeignKey(CustomerProfile, on_delete = models.CASCADE)
    ordered_on = models.DateTimeField(auto_now_add = True)

But I don’t know how to implement this in views.py
Any suggestion will be really helpful

Thank you

>Solution :

As per the current model relation you can use pre_save or post-save signals on ordered model. Whenever you update a new value(item added by buyer) in ordered_items(many-to-many relation) you can send a mail to seller linked with that buyer. That mailing part will be defined inside pre or post signals .

In views.py you will get input parameters as follows -:

• seller_id
• ordered_item
• buyer_id

And you will search for seller_id and buyer_id combination using filter statement in Ordered model and set ordered_item in that field. After that model save function will be called and after that post_save signal will be triggered and will send the mail to seller.

There will be 2 conditions for this scenario -:

1. Either you create a new value if user is buying his/her first item.
2. Buyer is adding another item in cart. In this case you will update the existing value.
   In Either case model’s save function will automatically be initiated.

Reference -:

• Pre-save and Post-save signals in django

• Django Official Documentation on signals