Question

我有三种模式：食物，膳食和膳食计划。

class Food(models.Model):
    name = models.CharField(max_length = 30, default="food")
    calories = models.FloatField(validators=[validate_positive])
    fat = models.FloatField(validators=[validate_positive])
    carbs = models.FloatField(validators=[validate_positive])
    protein = models.FloatField(validators=[validate_positive])

class Meal(models.Model):
    foods = models.ManyToManyField(Food)

    @property
    def totalcals(self):
        sum = self.foods.aggregate(models.Sum('calories'))['calories__sum']
        if sum == None:
            return 0
        else:
            return sum

class MealPlan(models.Model):
    meals = models.ManyToManyField(Meal)
    owner = models.CharField(max_length=14, default= "")

    @property
    def totalcals(self):
         sum = self.meals.foods.totalcals(models.Sum('totalcals'))['totalcals__sum']
        if sum == None:
            return 0
        else:
            return sum

第一个totalcals属性正常运行。第二个导致错误。我希望MealPlan中的第二个总膳食能够归还所有用餐总数。有没有办法做到这一点？

Answer 1

不应该是self.meals.totalcals ...而不是self.meals.foods.totalcals？食物不具有总膳食的特性，但是膳食确实如此。

@property
def totalcals(self):
  sum = self.meals.totalcals(models.Sum('totalcals'))['totalcals__sum']

Answer 2

怎么样？

@property
def totalcals(self):
   sum = 0
   for meal in self.meals.all():
       sum = sum + meal.totalcals

   if sum = 0:
       return None
   else:
       return sum

但我想也会有一个较短的答案。

在Django中访问嵌套的ManyToMany字段？

2 个答案: