Python Django rest框架：具有嵌套表示的PrimaryKeyRelatedField的行为

我有一个用django rest框架构建的API。 代码如下：

型号.py

class Ingredient(models.Model):
    barcode = models.CharField(max_length=13, primary_key=True)
    name = models.CharField(max_length=255)
    image = models.CharField(max_length=255)

class Recipe(models.Model):
    name = models.CharField(max_length=255)
    favorite = models.BooleanField()
    owner = models.ForeignKey(
        'auth.User', related_name="recipes", on_delete=models.CASCADE)

class Component(models.Model):
    ingredient = models.ForeignKey(Ingredient, on_delete=models.CASCADE)
    recipe = models.ForeignKey( Recipe, related_name='components', on_delete=models.CASCADE)
    quantity = models.FloatField()

class IngredientSerializer(serializers.ModelSerializer):
    name = serializers.CharField(read_only=True)
    image = serializers.CharField(read_only=True)

    class Meta:
        model = Ingredient
        fields = '__all__'

class ComponentSerializer(serializers.ModelSerializer):
    ingredient = serializers.PrimaryKeyRelatedField(queryset=Ingredient.objects.all())
    # ingredient = IngredientSerializer()
    class Meta:
        model = Component
        fields='__all__'

class RecipeSerializer(serializers.ModelSerializer):
    components = ComponentSerializer(many=True)
    owner = serializers.ReadOnlyField(source='owner.username')

    class Meta:
        model = Recipe
        fields = '__all__'

序列化程序.py

class Ingredient(models.Model):
    barcode = models.CharField(max_length=13, primary_key=True)
    name = models.CharField(max_length=255)
    image = models.CharField(max_length=255)

class Recipe(models.Model):
    name = models.CharField(max_length=255)
    favorite = models.BooleanField()
    owner = models.ForeignKey(
        'auth.User', related_name="recipes", on_delete=models.CASCADE)

class Component(models.Model):
    ingredient = models.ForeignKey(Ingredient, on_delete=models.CASCADE)
    recipe = models.ForeignKey( Recipe, related_name='components', on_delete=models.CASCADE)
    quantity = models.FloatField()

class IngredientSerializer(serializers.ModelSerializer):
    name = serializers.CharField(read_only=True)
    image = serializers.CharField(read_only=True)

    class Meta:
        model = Ingredient
        fields = '__all__'

class ComponentSerializer(serializers.ModelSerializer):
    ingredient = serializers.PrimaryKeyRelatedField(queryset=Ingredient.objects.all())
    # ingredient = IngredientSerializer()
    class Meta:
        model = Component
        fields='__all__'

class RecipeSerializer(serializers.ModelSerializer):
    components = ComponentSerializer(many=True)
    owner = serializers.ReadOnlyField(source='owner.username')

    class Meta:
        model = Recipe
        fields = '__all__'

代码处于这种状态时，我可以通过选择现有配料、现有配方并输入数量来创建新的成分。但是，组件的序列化不是嵌套的：

    {
        "id": 8,
        "quantity": 123.0,
        "ingredient": "3218930313023"
    },

当我在ComponentSerializer类中将代码更改为

component=IngredientSerializer（）

时，表示将按预期嵌套：

{
    "id": 9,
    "ingredient": {
        "barcode": "3218930313023",
        "name": "Crêpes L'Authentique",
        "image": "https://static.openfoodfacts.org/images/products/321/893/031/3023/front_fr.16.400.jpg",
    },
    "quantity": 123.0
}

但是，当我尝试添加具有现有配方和现有成分的成分时，我得到一个错误400，并显示以下消息：

{
    "ingredient": {
        "barcode": [
            "ingredient with this barcode already exists."
        ]
    }
}

要获得与第一个代码相同的添加组件的行为，但使用嵌套表示（如第二个代码）的最佳方法是什么

---

非常感谢您的帮助。

您正在使用条形码作为主键，这意味着它必须是唯一的，所以这就是您出现此错误的原因。但是我的条形码对于每种成分都是唯一的。是否可以实现这样一个事实，即如果带有条形码的成分已经存在，它将返回该成分，而不是尝试创建它？是的，您可以在视图中检查它是否已经存在，然后返回它，否则继续原始流。谢谢，我将尝试！