[英]why do we use the 'related_name' field as an attribute for a model field in django
在我的get_total_cost() function 下面的订单model 这是什么self.items ,它来自哪里?,我们通常在列表推导中给出一个可迭代的集合,但我没有在任何地方创建它。
这是我的models.py
from django.db import models
from shop.models import Product
class Order(models.Model):
first_name = models.CharField(max_length=50)
last_name = models.CharField(max_length=50)
email = models.EmailField()
address = models.CharField(max_length=250)
postal_code = model.CharField(max_length=20)
city = models.CharField(max_length=100)
created = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
paid = models.BooleanField(default=False)
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(Product, related_name='order_items', on_delete=modesl.CASCADE)
price = models.DecimalField(max_digits=10, decimal_places=2)
quantity = models.PositiveIntegerField(default=1)
def __str__(self):
return '{}'.format(self.id)
def get_cost(self):
return self.price * self.quantity
在我的get_total_cost() function 下面的订单model 这是什么self.items ,它来自哪里?,我们通常在列表推导中给出一个可迭代的集合,但我没有在任何地方创建它。
这是我的models.py
from django.db import models
from shop.models import Product
class Order(models.Model):
first_name = models.CharField(max_length=50)
last_name = models.CharField(max_length=50)
email = models.EmailField()
address = models.CharField(max_length=250)
postal_code = model.CharField(max_length=20)
city = models.CharField(max_length=100)
created = models.DateTimeField(auto_now_add=True)
updated = models.DateTimeField(auto_now=True)
paid = models.BooleanField(default=False)
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(Product, related_name='order_items', on_delete=modesl.CASCADE)
price = models.DecimalField(max_digits=10, decimal_places=2)
quantity = models.PositiveIntegerField(default=1)
def __str__(self):
return '{}'.format(self.id)
def get_cost(self):
return self.price * self.quantity
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