Django Rest 框架：嵌套序列化程序动态模型字段

Question

我已经定义了如下的序列化程序。我正在使用mixin 动态更改显示字段。

class SerializerTwo(serializers.ModelSerializer):

    class Meta:
        model = Two
        fields = ('name', 'contact_number')

class SerializerOne(DynamicFieldsModelSerializer, serializers.ModelSerializer):
    another_field = SerializerTwo()

    class Meta:
        lookup_field = 'uuid'
        model = One
        fields = ('status', 'another_field',)

现在我想要做的是，动态传递（即时）将从 SerializerTwo 使用的所有字段，就像我为 SerializerOne 所做的那样。

我为 SerializerOne 做的方式是：

# where fields=('status')
SerializerOne(queryset, fields=fields)

有没有办法，我可以将 SerializerTwo 中的字段添加到上面的 Serializer 初始化中。

# where fields=('status', 'name') name from SerializerTwo
# the double underscore notation does not work here for fields, so another_field__name cannot be used as well
SerializerOne(queryset, fields=fields)

Answer 1

我使用下面的方式来实现所谓的Nested Serializer Dynamic Model Fields。

class SerializerTwo(serializers.ModelSerializer):
    fields_filter_key = 'two_fields'
    class Meta:
        model = Two
        fields = ('name', 'contact_number')

class SerializerOne(DynamicFieldsModelSerializer, serializers.ModelSerializer):
    fields_filter_key = 'one_fields'
    another_field = serializers.SerializerMethodField()

    class Meta:
        lookup_field = 'uuid'
        model = One
        fields = ('status', 'another_field',)

    def get_another_field(self, obj):
        another_filed_serializer = SerializerTwo(obj.another_field, 
                                                 context=self.context)
        return another_filed_serializer.data 

我们对DynamicFieldsModelSerializer进行了一些修改

class DynamicFieldsModelSerializer(serializers.ModelSerializer):
    def __init__(self, *args, **kwargs):
        super(DynamicFieldsModelSerializer, self).__init__(*args, **kwargs)

        if 'request' not in self.context or not self.fields_filter_key:
            return
        fields = self.context['request'].query_params.get(self.fields_filter_key)
        if fields:
            fields = fields.split(',')
            allowed = set(fields)
            existing = set(self.fields.keys())
            for field_name in existing - allowed:
                self.fields.pop(field_name)

所以最后一个问题是如何组织url，这样写GET url：

domain/something?one_fields=name,contact_number&two_fields=another_field

Answer 2

在遇到同样的问题后，我找到了解决方案，希望这对某些人有所帮助。我修改了 DynamicFieldsModelSerializer 定义为here

def __init__(self, *args, **kwargs):
# Don't pass the 'fields' arg up to the superclass
fields = kwargs.pop('fields', None)
nested = kwargs.pop('nested', None)
# Instantiate the superclass normally
super(DynamicFieldsModelSerializer, self).__init__(*args, **kwargs)

if fields is not None:
    # Drop any fields that are not specified in the `fields` argument.
    allowed = set(fields)
    existing = set(self.fields.keys())
    for field_name in existing - allowed:
        self.fields.pop(field_name)

if nested is not None:
    for serializer in nested:
        try:
            nested_serializer = self.fields[serializer]
        except:
            logger.warning("Wrong nested serializer name")
            continue

        allowed = set(nested[serializer])
        existing = set(nested_serializer.fields.keys())
        for field_name in existing - allowed:
            nested_serializer.fields.pop(field_name)

之后，你可以这样使用它：

SerializerOne(queryset, nested={"another_field": ["name"]})

您可以修改我的解决方案以使用双下划线而不是另一个带有 dict 的 kewyord，但我想将常规字段与嵌套序列化程序分开。

还可以改进为递归，这里我只处理一个嵌套序列化器的深度

编辑 毕竟我修改了我的代码以使用双下划线语法：

def __init__(self, *args, **kwargs):

    def parse_nested_fields(fields):
        field_object = {"fields": []}
        for f in fields:
            obj = field_object
            nested_fields = f.split("__")
            for v in nested_fields:
                if v not in obj["fields"]:
                    obj["fields"].append(v)
                if nested_fields.index(v) < len(nested_fields) - 1:
                    obj[v] = obj.get(v, {"fields": []})
                    obj = obj[v]
        return field_object

    def select_nested_fields(serializer, fields):
        for k in fields:
            if k == "fields":
                fields_to_include(serializer, fields[k])
            else:
                select_nested_fields(serializer.fields[k], fields[k])

    def fields_to_include(serializer, fields):
        # Drop any fields that are not specified in the `fields` argument.
        allowed = set(fields)
        existing = set(serializer.fields.keys())
        for field_name in existing - allowed:
            serializer.fields.pop(field_name)

    # Don't pass the 'fields' arg up to the superclass
    fields = kwargs.pop('fields', None)
    # Instantiate the superclass normally
    super(DynamicFieldsModelSerializer, self).__init__(*args, **kwargs)

    if fields is not None:
        fields = parse_nested_fields(fields)
        # Drop any fields that are not specified in the `fields` argument.
        select_nested_fields(self, fields)

然后你可以像这样使用它：

SerializerOne(instance, fields=["another_field__name"])

Answer 3

@Lotram 的答案不适用于返回多个值的字段（通过many=True）。

以下代码改进了 @Lotram 的解决方案，该解决方案适用于返回多个值的字段：

class NestedDynamicFieldsModelSerializer(serializers.ModelSerializer):

def __init__(self, *args, **kwargs):

    def parse_nested_fields(fields):
        field_object = {"fields": []}
        for f in fields:
            obj = field_object
            nested_fields = f.split("__")
            for v in nested_fields:
                if v not in obj["fields"]:
                    obj["fields"].append(v)
                if nested_fields.index(v) < len(nested_fields) - 1:
                    obj[v] = obj.get(v, {"fields": []})
                    obj = obj[v]
        return field_object

    def select_nested_fields(serializer, fields):
        for k in fields:
            if k == "fields":
                fields_to_include(serializer, fields[k])
            else:
                select_nested_fields(serializer.fields[k], fields[k])

    def fields_to_include(serializer, fields):
        # Drop any fields that are not specified in the `fields` argument.
        allowed = set(fields)
        if isinstance(serializer, serializers.ListSerializer):
            existing = set(serializer.child.fields.keys())
            for field_name in existing - allowed:
                serializer.child.fields.pop(field_name)
        else:
            existing = set(serializer.fields.keys())
            for field_name in existing - allowed:
                serializer.fields.pop(field_name)

    # Don't pass the 'fields' arg up to the superclass
    fields = kwargs.pop('fields', None)
    # Instantiate the superclass normally
    super(NestedDynamicFieldsModelSerializer, self).__init__(*args, **kwargs)

    if fields is not None:
        # import pdb; pdb.set_trace()
        fields = parse_nested_fields(fields)
        # Drop any fields that are not specified in the `fields` argument.
        select_nested_fields(self, fields)