Django聚合

Question

大家好我想创建一个发票。为此我使用django聚合来总结工作时间。代码如下：

class ProjectTask(models.Model):

    project_info = models.ForeignKey(ProjectInvitation, blank=True)
    name = models.CharField(max_length=50)
    description = models.TextField()
    scm_id = models.CharField(max_length=10, blank=True, null=True)
    estimated_hours = models.DecimalField(max_digits=10,
    decimal_places=2)
    percent_completed = models.DecimalField(max_digits=10,
    decimal_places=2)
    worked_hours = models.DecimalField(max_digits=10,
    decimal_places=2)

    def save(self, *args, **kwargs):
      worked_hours = self.estimated_hours * self.percent_completed 
      super(ProjectTask, self).save(*args, **kwargs)

total = ProjectTask.objects.all().aggregate(Sum('worked_hours'))

问题是我得到RuntimeError（“App注册表还没有准备好。”）。任何想法如何克服它？

Answer 1

聚合没有问题。

参见文档： https://docs.djangoproject.com/en/1.7/releases/1.7/#app-loading-changes