m2m change for calculate product update - lhmisho/django-eCommerce GitHub Wiki

Creating signal on models

carts/models.py

from django.db import models
from django.conf import settings
from products.models import Product
from django.db.models.signals import m2m_changed, pre_save
# Create your models here.

User = settings.AUTH_USER_MODEL

class CartManager(models.Manager):

    # creating cart object on model so that we can use it where ever we neeed
    def new_or_get(self, request):
        cart_id = request.session.get("cart_id", None)
        qs = self.get_queryset().filter(id=cart_id)

    # if the id is exits than go else create one
        if qs.count() == 1:
            new_obj = False
            cart_obj = qs.first()
            if request.user.is_authenticated and cart_obj.user is None:
                cart_obj.user = request.user
                cart_obj.save()
        else:
            # if there is some issue than it's might me ( cart_obj = self.new_cart(user=request.user) )
            cart_obj = Cart.new_cart(user=request.user)
            new_obj = True
            request.session['cart_id'] = cart_obj.id

        return cart_obj, new_obj
    def new_cart(self, user=None):
        print(user)
        user_obj = None
        if user is not None:
            if user.is_authenticated:
                user_obj = user
        return self.model.objects.create(user=user_obj)

class Cart(models.Model):
    user        = models.ForeignKey(User, null=True, blank=True, on_delete=models.CASCADE)
    products    = models.ManyToManyField(Product, blank=True)
    subtotal    = models.DecimalField(default=0.00, decimal_places=2, max_digits=100)
    total       = models.DecimalField(default=0.0, decimal_places=2, max_digits=100)
    updated     = models.DateTimeField(auto_now=True)
    timestamp   = models.DateTimeField(auto_now_add=True)

    objects = CartManager()

    def __str__(self):
        return str(self.id)

def m2m_changed_cart_receiver(sender, instance, action, *args, **kwargs):
    # print(action)
    # print(instance.products.all())
    # print(instance.total)
    #if action == 'post_add' or action == 'post_remove' or action == 'post_clear':
    products = instance.products.all()
    total = 0
    for x in products:
        total += x.price
    if instance.subtotal != total:
        instance.subtotal = total
        instance.save()
    print(total)
m2m_changed.connect(m2m_changed_cart_receiver, sender=Cart.products.through)

def pre_save_cart_receiver(sender, instance, *args, **kwargs):
    instance.total = instance.subtotal + 10

pre_save.connect(pre_save_cart_receiver, sender=Cart)

here i added m2m_changed and pre_save for calculate data to many to many field and pre_save for totaling

#################################################################################
# creating signal so that we can calculate our products at the time of shopping
def m2m_changed_cart_receiver(sender, instance, action, *args, **kwargs):
    # print(action)
    # print(instance.products.all())
    # print(instance.total)
    #if action == 'post_add' or action == 'post_remove' or action == 'post_clear':
    products = instance.products.all()
    total = 0
    for x in products:
        total += x.price
    if instance.subtotal != total:
        instance.subtotal = total
        instance.save()
    print(total)
m2m_changed.connect(m2m_changed_cart_receiver, sender=Cart.products.through)

# calculating subtotal like delevary cost etc .....
def pre_save_cart_receiver(sender, instance, *args, **kwargs):
        instance.total = instance.subtotal + 10
pre_save.connect(pre_save_cart_receiver, sender=Cart)
############################################################

managing views

carts/views.py

from django.shortcuts import render
from .models import Cart

# Create your views here.

# method for create a cart for user.

def cart_home(request):
    cart_obj, new_obj = Cart.objects.new_or_get(request)
    return render(request, 'carts/cart_home.html', {})