如何检查Django rest框架中的数据是否存在

问题描述

我有一个CartModel，CartItem模型。我尝试在创建购物车时创建该购物车，并在创建该购物车时再次添加与我在以前输入的数据相同的数据，以创建另一个购物车。 我试图这样做，如果CartItem表中存在购物车，它必须显示响应“购物车已存在”。 但它正在创建另一个购物车。我进行了大量搜索并使用了代码，但该代码无法运行。 如果有人能够给出答案，请帮助我。

views.py *

class CartTestViewSet(viewsets.ModelViewSet):
    serializer_class = CartItemSerializer
    permission_classes = (IsAuthenticated,)
    
    def get_queryset(self):
        user = self.request.user
        if user.is_authenticated:
            if user is not None:
                if user.is_active and user.is_superuser or user.is_Customer:
                    return CartItem.objects.all()
                raise PermissionDenied()
            raise PermissionDenied()
        raise PermissionDenied()

    def post(self,request):       
        cart = Cart.objects.filter(user=request.user,cart=request.data,service=request.data,defects=request.data)
        if cart.exists():   
            print('cart already exists')
        else:
            print('cart is created')

serializers.py

from rest_framework import serializers
from .models import CartItem,CartModel
from rest_framework.response import Response

class CartItemSerializer(serializers.ModelSerializer):
    def get_total(self,obj):
        return obj.get_total
    get_total = serializers.IntegerField(read_only=True,required=False)
    # id = serializers.IntegerField(read_only=False)
    class Meta:
        model = CartItem
        fields = "__all__"
        extra_fields = ['get_total']
        read_only = ['get_total']

class CartModelSerializer(serializers.ModelSerializer):
    class Meta:
        model = CartModel
        fields = "__all__"

models.py

from django.db import models
from accounts.models import User,SubCategory
from category.models import defects
from django.utils import timezone
# Create your models here.

class CartModel(models.Model):
    user = models.ForeignKey('accounts.User',on_delete=models.CASCADE)
    status_choice = [
        ('1','open'),('2','closed')
    ]
    status = models.CharField(max_length=2,choices=status_choice,default=1)
    
    def __str__(self):
        return self.user.username
    
class CartItem(models.Model):
    cart = models.ForeignKey('CartModel',on_delete=models.CASCADE)
    user = models.ForeignKey('accounts.User',on_delete=models.CASCADE)
    service = models.ForeignKey('accounts.SubCategory',on_delete=models.CASCADE)
    defects = models.ForeignKey('category.defects',on_delete=models.CASCADE)
    quantity = models.IntegerField(default=1)
    price = models.IntegerField()
    created_on = models.DateTimeField(auto_Now_add=True)
    updated_on = models.DateTimeField(auto_Now_add=True)


    def __str__(self):
        total = int(self.quantity) * int(self.price)
        return str(total)

    
    def get_total(self):
        total = int(self.quantity )* int(self.price)
        return total

解决方法

您可以在CartItem模型中使用unique=True。 如果您尝试以此保存重复的值，django将引发错误。

cart = models.ForeignKey('CartModel',on_delete=models.CASCADE,unique=True)