Django REST 框架 : direct assignment to the forward side of a many-to-many set is prohibited

Question

我有一个配方和成分类，我在成分模型上放置了一个 m2m。我在管理面板中测试了模型并且工作正常。但是，当我尝试在 shell 中创建它们时，出现错误(请参阅下面的错误)。

class Ingredient(models.Model):
    name = models.CharField(max_length=50)
    amount = models.IntegerField(default=1)
    ingredients = models.ManyToManyField(Recipe, related_name='ingredients')


class IngredientSerializer(ModelSerializer):
    class Meta:
        fields = ['name', 'amount']
        model = Ingredient



class Recipe(models.Model):
    owner = models.ForeignKey('auth.User', related_name='recipes', on_delete=models.CASCADE)
    name = models.CharField(max_length=100)
    description = models.TextField(max_length=200, blank=True)
    image = models.CharField(max_length=100, blank=True)


class RecipeSerializer(ModelSerializer):
        ingredients = IngredientSerializer(many=True)
        owner = ReadOnlyField(source='owner.username')

    class Meta:
        fields = ['owner', 'name', 'description', 'image', 'ingredients']
        model = Recipe

Shell 命令

beefsoup = Recipe.objects.create(owner=user, name="beef", description="goot", image="httplo")
tomatoes = Ingredient.objects.create(ingredients=beefsoup ,name='tomatoes', amount=2)

错误
类型错误:禁止直接分配给多对多集合的前端。改用成分.set()。

Answer 1

作为错误信息和 Django Docs建议，您的代码段应如下所示:

  beefsoup = Recipe.objects.create(owner=user, name="beef", description="goot", image="httplo")
  beefsoup.ingredients.create(name='tomatoes', amount=2)

除此之外，从模型和属性名称来看，您的关系设计似乎不正确。它应该看起来像这样:

class Ingredient(models.Model):
    name = models.CharField(max_length=50)
    amount = models.IntegerField(default=1)


class IngredientSerializer(ModelSerializer):
    class Meta:
        fields = ['name', 'amount']
        model = Ingredient


class Recipe(models.Model):
    owner = models.ForeignKey('auth.User', related_name='recipes', on_delete=models.CASCADE)
    name = models.CharField(max_length=100)
    description = models.TextField(max_length=200, blank=True)
    image = models.CharField(max_length=100, blank=True)
    ingredients = models.ManyToManyField(Ingredients, related_name='recipes')


class RecipeSerializer(ModelSerializer):
    ingredients = IngredientSerializer(many=True)
    owner = ReadOnlyField(source='owner.username')

    class Meta:
        fields = ['owner', 'name', 'description', 'image', 'ingredients']
        model = Recipe

请注意 ingredients现居 Recipe模型。