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Django Rest框架:如何将数据传递给嵌套序列化程序并仅在自定义验证之后创建对象

django-serializer django-views django-rest-framework django-models django

Sreekanth Reddy Balne · 技术社区 · 6 年前

我有两个模型:

class Book(AppModel):
    title = models.CharField(max_length=255)

class Link(AppModel):
    link = models.CharField(max_length=255)

class Page(AppModel):
    book= models.ForeignKey("Book",related_name="pages",on_delete=models.CASCADE)
    link = models.ForeignKey("Link", related_name="pages", on_delete=models.CASCADE)
    page_no = models.IntegerField()
    text = models.TextField()

和 serializers

class LinkSerializer(serializers.ModelSerializer):
    class Meta:
       model = Link
       fields = ['link']

class PageSerializer(serializers.ModelSerializer):
    class Meta:
        model = Page
        fields = ('link','text','page_no')

    def validate_text(self, value):
        #some validation is done here.

    def validate_link(self, value):
        #some validation is done here.

class BookSerializer(serializers.ModelSerializer):
    pages = PageSerializer(many=True)
    class Meta:
        model = Book
        fields = ('title','pages')

    @transaction.atomic
    def create(self, validated_data):
        pages_data= validated_data.pop('pages')
        book = self.Meta.model.objects.create(**validated_data)
        for page_data in pages_data:
            Page.objects.create(book=book, **page_data)
        return book

有一个 validate_text PageSerializer . 这个 create 方法永远不会调用 页面序列化程序 以及 page_data

所以我尝试了另一种方法:

@transaction.atomic
def create(self, validated_data):
    pages_data = validated_data.pop('pages')
    book= self.Meta.model.objects.create(**validated_data)
    for page_data in pages_data:
        page = Page(book=book)
        page_serializer = PageSerializer(page, data = page_data)
        if page_serializer.is_valid():
            page_serializer.save()
        else:
            raise serializers.ValidationError(page_serializer.errors)
    return book

{
"title": "Book Title",
"pages": [{
"link":1,"page_no":52, "text":"sometext"}]
}

但上述方法会产生错误:

{
"link": [
    "Incorrect type. Expected pk value, received Link."
    ]
}

pk 价值 1 的 Link ,将数据传递到从 BookSerializer 如下所示: {"link": "/go_to_link/", "page_no":52, "text": "sometext"}

链接 传递给 页面序列化程序 而我送的是 主键 属于 ? 这里需要帮助。

2 回复 | 直到 6 年前

Tolqinbek Isoqov 6 年前

当你打电话的时候 serializer.is_valid(raise_exception=True/False) 它自动调用嵌套序列化程序的validate函数。当你打电话的时候 serializer.save(**kwargs) 序列化程序将经过验证的数据传递到 create(self, validated_data) 或 update(self, instance, validated_data) 序列化程序的函数。此外,在经过验证的数据中,ForeignKey字段返回了一个对象。

def create(self, validated_data):
    pages_data = validated_data.pop('pages') # [{'link': Linkobject, ...}]
    book= self.Meta.model.objects.create(**validated_data)
    for page_data in pages_data:
        page = Page(book=book)
        page_serializer = PageSerializer(page, data = page_data) # here you are sending object to validation again
        if page_serializer.is_valid():
            page_serializer.save()
        else:
            raise serializers.ValidationError(page_serializer.errors)
    return book

Sreekanth Reddy Balne 6 年前

要使用嵌套序列化程序验证嵌套对象,请执行以下操作:

@transaction.atomic
def create(self, validated_data):
    pages_data = validated_data.pop('pages') #pages data of a book
    book= self.Meta.model.objects.create(**validated_data)
    for page_data in pages_data:
        page = Page(book=book)
        page_serializer = PageSerializer(page, data = page_data)
        if page_serializer.is_valid(): #PageSerializer does the validation
            page_serializer.save()
        else:
            raise serializers.ValidationError(page_serializer.errors) #throws errors if any
    return book

假设您将数据发送为:

{
    "title": "Book Title",
    "pages": [{
        "link":2,#<= this one here
        "page_no":52, 
        "text":"sometext"}]
}

在上述数据中,我们发送了一个 id 的 Link 对象。但是在 create 方法 BookSerializer 我们将更改发送到的数据定义如下:

{
    "title": "Book Title",
    "pages": [{
        "link":Link Object (2),#<= changed to the Link object with id 2
        "page_no":52, 
        "text":"sometext"}]
}

以及 PageSerializer 实际上是要接受 pk 价值 link 即, "link": 2 而不是 "link":Link Object (2)

{ "link": [ "Incorrect type. Expected pk value, received Link." ] }

所以解决方法是重写 to_internal_value 方法来转换接收到的 Link Object (2) 反对其 主键 价值观。

所以你的 页面序列化程序

class PageSerializer(serializers.ModelSerializer):
    class Meta:
        model = Page
        fields = ('link','text','page_no')

    def to_internal_value(self, data): 
        link_data = data.get("link")
        if isinstance(link_data, Link): #if object is received
            data["link"] = link_data.pk # change to its pk value
        obj = super(PageSerializer, self).to_internal_value(data)
        return obj

    def validate_text(self, value):
        #some validation is done here.

    def validate_link(self, value):
        #some validation is done here.

以及父序列化程序:

class BookSerializer(serializers.ModelSerializer):
    pages = PageSerializer(many=True)
    class Meta:
        model = Book
        fields = ('title','pages')

    @transaction.atomic
    def create(self, validated_data):
        pages_data = validated_data.pop('pages')#pages data of a book
        book= self.Meta.model.objects.create(**validated_data)
        for page_data in pages_data:
            page = Page(book=book)
            page_serializer = PageSerializer(page, data = page_data)
            if page_serializer.is_valid(): #PageSerializer does the validation
                page_serializer.save()
            else:
                raise serializers.ValidationError(page_serializer.errors) #throws errors if any
        return book

这应该允许嵌套的序列化程序执行验证,而不是在父序列化程序的create方法中写入验证,并进行验证。