我想创建一个字段名称: total ,其中包含所有产品的总价格*数量。我想要的是如何在Django模型中进行total = price*quantity
。如您所见,可能有不止一种产品。
我通过tabularinline将OderItem模型与Order一起加入。
class OrderItemInline(admin.TabularInline):
model = OrderItem
raw_id_fields = ['product']
class OrderAdmin(admin.ModelAdmin):
list_display = ['id','name', 'mobile_no','address','status', 'created']
list_editable = ['status']
list_per_page = 15
list_filter = ['status']
search_fields = ('id',)
inlines = [OrderItemInline]
admin.site.register(Order, OrderAdmin)
class Order(models.Model):
name = models.CharField(max_length=60)
email = models.EmailField(max_length=60,default=None, blank=True)
mobile_no = models.CharField(max_length=13, default=None)
address = models.CharField(max_length=150)
created = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
status_choices = (
('In Queue', 'In Queue'),
('Processing', 'Processing'),
('Ready', 'Ready'),
('Delivered', 'Delivered'),
('Paid', 'Paid'),
('Cancelled', 'Cancelled'),
)
status = models.CharField(max_length=15, choices=status_choices, default=status_choices[0][0])
class Meta:
ordering = ('created', )
def __str__(self):
return 'Order {}'.format(self.id)
def get_total_cost(self):
return sum(item.get_cost() for item in self.items.all())
class OrderItem(models.Model):
order = models.ForeignKey(Order, related_name='items',
on_delete=models.CASCADE)
product = models.ForeignKey(MenuVariant, related_name='order_items',
on_delete=models.CASCADE, default=None)
size = models.CharField(max_length=20, default=None)
price = models.DecimalField(max_digits=10, decimal_places=2)
quantity = models.PositiveIntegerField(default=1)
# total = models.DecimalField(max_digits=10, decimal_places=2,default=0)
def __str__(self):
return '{}'.format(self.id)
def get_cost(self):
return self.price * self.quantity
答案 0 :(得分:1)
您可以直接通过数据库查询获得Order
的总价,因此无需将其保存在数据库中:
from django.db.models import Sum, F, FloatField
orders = Order.objects.annotate(total=Sum(F('items__quantity')*F('items__price'), output_field=FloatField()))
这将向每个查询结果添加一个total
字段。然后:
price_of_first_order = orders.first().total
如果您想在管理中显示order
的总数,请对ModelAdmin
进行子类化,并将get_total_cost
添加到readonly_fields
中,如{{3}所述。 }:
一个只读字段不仅可以显示模型字段中的数据,还可以显示模型方法的输出或ModelAdmin类本身的方法。这与ModelAdmin.list_display的行为非常相似。
答案 1 :(得分:1)
虽然我像dirkgroten一样不太了解将值保存在模型字段中的意义,但您可以在total=models.IntegerField(null=True, blank=True)
模型中添加字段Order
并使用post_save
更新值。
因此,由于您已经拥有get_total_cost()
,因此我们可以执行以下操作:
def order_pre_save(sender, instance, **kwargs):
instance.total_cost = instance.get_total_cost()
pre_save.connect(order_pre_save, sender=Order)
编辑:正如dirkgroten指出的那样,您需要在post_save
上使用OrderItem
:
def order_item_pre_save(sender, instance, **kwargs):
instance.order.total_cost = instance.order.get_total_cost()
instance.order.save()
post_save.connect(order_item_pre_save, sender=OrderItem)
您还需要在删除时更新值:
def order_item_pre_delete(sender, instance, **kwargs):
instance.order.total_cost = instance.order.get_total_cost() - instance.get_cost()
instance.order.save()
post_delete.connect(order_item_pre_delete, sender=OrderItem)