Question

我有这些模特：

#model.py

class Subject(models.Model):
    name = models.CharField("Name",max_length=50, blank=True)
    ...
    ...

class Activity(models.Model):
    label = models.CharField("Act. name",max_length=150)
    price = models.DecimalField("price", max_digits=10, decimal_places=2,default=0)
    count = models.IntegerField("Count", default=0)

    def __unicode__(self):
        return u"%s" % (self.label)
    class Meta:
        verbose_name_plural = "Activities"


class Invoice(models.Model):
    subject = models.ForeignKey(Subject)
    date = models.DateField(default=date.today())
    activities = models.ManyToManyField(Activity)
    ....
    ....

在admin上创建一个新的Invoice实例时，我可以选择多个到多个字段的“活动”，但是我希望有一个额外的计数器（例如，一个IntegerField）作为Invoice字段来计算和保存数量每个活动添加到我的Invoice实例中。这可能吗？

感谢，

路

Answer 1

你可以在模型上有一个字段并覆盖保存方法

class Invoice(models.Model):
    subject = models.ForeignKey(Subject)
    date = models.DateField(default=date.today())
    activities = models.ManyToManyField(Activity)
    activity_count = models.PositiveIntegerField(default=0)
    def save(self):
       self.activity_count = self.activities.count()
       super(Invoice, self).save()

django - 为每个添加的ManyToMany字段添加一个计数器

1 个答案: