Django模式保存覆盖更简单的方法？ [英] Django Model Save Override Simpler Approach?

问题描述

我想覆盖我的模型的保存方法，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（从我的模型）：

I'm looking to override the save method of my model so that it does some simple calculations before saving, then saves the final result. Calculation example(from my model):

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

尽管我已经能够完成它，我很想知道是否有是完成相同的替代方法。

Although I have been able to accomplish it, I would love to know if there are alternative simpler methods to accomplish the same.

查看我的models.py，你会明白我的意思

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

推荐答案

正如@karthinkr在评论中所说，你可以使用 pre_save 。这里有一个例子：

As @karthinkr says in comments, you could use pre_save. Here an example:

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)

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