Question

我希望覆盖模型的save方法，以便在保存之前进行一些简单的计算，然后保存最终结果。计算示例（来自我的模型）：

total_ticket = ticket2 - ticket1
gross_sales = rate * total_ticket
total_tax = tax * total_ticket

虽然我已经能够完成它，但我很想知道是否有其他更简单的方法来实现它。

看看我的models.py，你明白我的意思

class Entry(models.Model):
    ticket1 = models.IntegerField()
    ticket2 = models.IntegerField()
    total_ticket = models.IntegerField(default=0, editable=False)
    rate = models.IntegerField(null=True, blank=True)
    tax = models.IntegerField(null=True, blank=True)
    gross_sales = models.IntegerField(default=0, editable=False)
    total_tax = models.IntegerField(default=0, editable=False)

    def save(self, *args, **kwargs):
        # calculate sum before saving.
        self.total_ticket = self.calculate_ticket()
        self.gross_sales = self.calculate_gross_sales()
        self.total_tax = self.calculate_tax()
        super(Entry, self).save(*args, **kwargs)

    def calculate_gross_sales(self):
        try:
            total_ticket = self.total_ticket
            rate = self.rate
            return total_ticket * rate
        except KeyError:
            return 0

    def calculate_tax(self):
        try:
            total_ticket = self.total_ticket
            tax = self.tax
            return total_ticket * tax
        except KeyError:
            return 0

    def calculate_ticket(self):
        """ Calculate a numeric value for the model instance. """
        try:
            ticket1 = self.ticket1
            ticket2 = self.ticket2
            return ticket2 - ticket1
        except KeyError:
            return 0

    def __str__(self):
        return self.show

Answer 1

正如@karthinkr在评论中所说，你可以使用pre_save。这是一个例子：

from django.db.models.signals import pre_save

def calculate_things(sender, instance, **kwargs):
    # sender => Model
    # instance => Object pre saved
    ...
    # Your loginc here

class Entry(models.Model):
    ...
    # Model definition
    ...

    ... # You don't need re define save method.


pre_save.connect(calculate_things, sender=Entry)

Django模型保存覆盖更简单的方法？

1 个答案: