python - 将 Django 模型中两个对象的值相乘

Question

嘿，我正在处理一个 Django 项目，我想在其中将 django 模型中两个不同对象的值相乘并将其存储到数据库中。

这是我的模型代码

from django.db import models
from django.utils import timezone
from master.models import Supplier

class RawItem(models.Model):
    item_code = models.AutoField(primary_key=True)
    item_name = models.CharField(max_length=100)
    item_price = models.PositiveIntegerField()
    item_Description = models.TextField()

    def __str__(self):
        return self.item_name

class PurchaseOrder(models.Model):
    raw_item = models.ForeignKey(RawItem, on_delete=models.CASCADE)
    quantity = models.PositiveIntegerField()
    total_prize = models.PositiveIntegerField(editable=False, blank=True, null=True)
    po_date = models.DateTimeField(default=timezone.now)
    supplier = models.ForeignKey(Supplier, on_delete=models.CASCADE)

    def save(self, *args, **kwargs):
        total_prize = self.raw_item.item_price * self.quantity
        super(PurchaseOrder, self).save(*args, **kwargs)

所以在这里我想将 item_price 与数量相乘如何做到这一点预先感谢您

Answer 1

要设置当前实例的total_prize，您应该使用self。对于您的情况:

def save(self, *args, **kwargs):
    self.total_prize = self.raw_item.item_price * self.quantity
    #^^^
    super(PurchaseOrder, self).save(*args, **kwargs)

您可以阅读更多详情understand self in python

以及 class-objects 的官方文档