Django REST框架：在ModelViewSet中保存相关模型

Question

我试图弄清楚如何使用 Django REST 框架保存相关模型。 在我的应用程序中，我有一个模型 Recipe 和 2 个相关模型：RecipeIngredient 和 RecipeStep。 Recipe 对象必须至少有 3 个相关的 RecipeIngredient 和 3 个 RecipeStep。在引入 REST 框架之前，我使用带有两个表单集的 Django CreateView，保存过程如下（遵循 form_valid() 的代码）：

def save_formsets(self, recipe):
    for f in self.get_formsets():
        f.instance = recipe
        f.save()

def save(self, form):
    with transaction.atomic():
        recipe = form.save()
        self.save_formsets(recipe)
    return recipe

def formsets_are_valid(self):
        return all(f.is_valid() for f in self.get_formsets())

def form_valid(self, form):
    try:
        if self.formsets_are_valid():
            try:
                return self.create_ajax_success_response(form)
            except IntegrityError as ie:
                return self.create_ajax_error_response(form, {'IntegrityError': ie.message})
    except ValidationError as ve:
        return self.create_ajax_error_response(form, {'ValidationError': ve.message})
    return self.create_ajax_error_response(form)

现在我有我的RecipeViewSet：

class RecipeViewSet(ModelViewSet):
    serializer_class = RecipeSerializer
    queryset = Recipe.objects.all()
    permission_classes = (RecipeModelPermission, )

使用RecipeSerializer:

class RecipeSerializer(serializers.ModelSerializer):
    class Meta:
        model = Recipe
        fields = (
            'name', 'dish_type', 'cooking_time', 'steps', 'ingredients'
        )

    ingredients = RecipeIngredientSerializer(many=True)
    steps = RecipeStepSerializer(many=True)

这些是相关的序列化程序：

class RecipeIngredientSerializer(serializers.ModelSerializer):
    class Meta:
        model = RecipeIngredient
        fields = ('name', 'quantity', 'unit_of_measure')

class RecipeStepSerializer(serializers.ModelSerializer):
    class Meta:
        model = RecipeStep
        fields = ('description', 'photo')

现在...我应该如何验证相关模型（RecipeIngredient 和 RecipeStep）并在调用 RecipeViewSet 的 create() 方法时保存它们？ （RecipeSerializer 中的is_valid() 实际上忽略了嵌套关系，只报告与主模型相关的错误Recipe）。 目前我试图覆盖RecipeSerializer中的is_valid()方法，但不是那么简单......有什么想法吗？

Answer 1

本周我正在处理类似的问题，我发现 django rest 框架 3 实际上支持嵌套可写序列化（http://www.django-rest-framework.org/topics/3.0-announcement/#serializers 在子章可写嵌套序列化中。）

我不确定嵌套的序列化器是否默认可写，所以我声明了它们：

ingredients = RecipeIngredientSerializer(many=True, read_only=False)
steps = RecipeStepSerializer(many=True, read_only=False)

你应该在 RecipeSerializer 中重写你的创建方法：

class RecipeSerializer(serializers.ModelSerializer):
    ingredients = RecipeIngredientSerializer(many=True, read_only=False)
    steps = RecipeStepSerializer(many=True, read_only=False)

    class Meta:
        model = Recipe
        fields = (
            'name', 'dish_type', 'cooking_time', 'steps', 'ingredients'
        )

    def create(self, validated_data):
        ingredients_data = validated_data.pop('ingredients')
        steps_data = validated_data.pop('steps')
        recipe = Recipe.objects.create(**validated_data)
        for ingredient in ingredients_data:
            #any ingredient logic here
            Ingredient.objects.create(recipe=recipe, **ingredient)
        for step in steps_data:
            #any step logic here
            Step.objects.create(recipe=recipe, **step)
        return recipe

如果这种结构 Step.objects.create(recipe=recipe, **step) 不起作用，也许您必须从​​ steps_data / ingredients_data 中选择代表每个字段的数据。

这是我之前在堆栈上的（真实的）问题/答案的链接：How to create multiple objects (related) with one request in DRF?

Answer 2

我想我得到了答案。

类 RecetaSerializer(serializers.ModelSerializer):

ingredientes = IngredientesSerializer(many=True, partial=True)
autor = serializers.PrimaryKeyRelatedField(queryset=User.objects.all())
depth = 2

class Meta:
    model = Receta
    fields = ('url','pk','nombre','foto','sabias_que','ingredientes','pasos','fecha_publicacion','autor')   

def to_internal_value(self,data):

    data["fecha_publicacion"] = timezone.now()
    ingredientes_data = data["ingredientes"]

    for ingrediente in ingredientes_data:

        alimento_data = ingrediente["alimento"]

        if Alimento.objects.filter(codigo = alimento_data['codigo']).exists():

            alimento = Alimento.objects.get(codigo= alimento_data['codigo'])              
            ingrediente["alimento"] = alimento

        else:
            alimento = Alimento(codigo = alimento_data['codigo'], nombre = alimento_data['nombre'])
            alimento.save()                
            ingrediente["alimento"] = alimento
    data["ingredientes"] = ingredientes_data
    return data

def create(self, validated_data):

    ingredientes_data = validated_data.pop('ingredientes')

    receta_data = validated_data
    usuario = User.objects.get(id = validated_data["autor"])
    receta_data['autor'] = usuario

    receta = Receta.objects.create(**validated_data)


    for ingrediente in ingredientes_data:

        alimento_data = ingrediente["alimento"]
        ingrediente = Ingredientes(receta= receta, cantidad = ingrediente['cantidad'], unidad = ingrediente['unidad'], alimento = alimento_data)
        ingrediente.save()

    receta.save()


    return receta

重写 to_internal_value() 很重要。我遇到了函数 is_valid() 的问题。所以在函数 to_internal_value() 中所做的每一次更改都在函数 is_valid() 之前