Django REST Framework嵌套对象：POST与DELETE字段必填规则配置

方案1：动态控制UserSerializer的字段必填性 #

给UserSerializer添加初始化参数，根据传入的参数动态调整字段的required属性，让同一个序列化器适配不同场景：

class UserSerializer(serializers.Serializer):
    email = serializers.EmailField(required=True)
    username = serializers.CharField(max_length=100, required=True)

    def __init__(self, *args, **kwargs):
        # 接收自定义参数，默认同时校验两个字段
        required_fields = kwargs.pop('required_fields', ['email', 'username'])
        super().__init__(*args, **kwargs)
        
        # 只将指定字段设为必填，其余改为非必填
        for field_name in self.fields:
            self.fields[field_name].required = field_name in required_fields

class PostCommentSerializer(serializers.Serializer):
    # 发布评论时仅校验username必填
    user = UserSerializer(required=True, required_fields=['username'])

class DeleteCommentSerializer(serializers.Serializer):
    # 删除评论时仅校验email必填
    user = UserSerializer(required=True, required_fields=['email'])

方案2：创建UserSerializer的场景子类 #

针对不同业务场景，定义UserSerializer的子类，各自指定必填字段，逻辑更直观：

class BaseUserSerializer(serializers.Serializer):
    # 基础序列化器，定义所有字段但不强制必填
    email = serializers.EmailField(required=False)
    username = serializers.CharField(max_length=100, required=False)

class PostUserSerializer(BaseUserSerializer):
    # 发布评论场景：仅username必填
    username = serializers.CharField(max_length=100, required=True)

class DeleteUserSerializer(BaseUserSerializer):
    # 删除评论场景：仅email必填
    email = serializers.EmailField(required=True)

class PostCommentSerializer(serializers.Serializer):
    user = PostUserSerializer(required=True)

class DeleteCommentSerializer(serializers.Serializer):
    user = DeleteUserSerializer(required=True)

方案3：在父序列化器中自定义校验逻辑 #

如果不想修改UserSerializer，可以在父序列化器的字段校验方法里手动校验嵌套字段：

class UserSerializer(serializers.Serializer):
    email = serializers.EmailField(required=False)
    username = serializers.CharField(max_length=100, required=False)

class PostCommentSerializer(serializers.Serializer):
    user = UserSerializer(required=True)

    def validate_user(self, value):
        if not value.get('username'):
            raise serializers.ValidationError('username为必填项')
        return value

class DeleteCommentSerializer(serializers.Serializer):
    user = UserSerializer(required=True)

    def validate_user(self, value):
        if not value.get('email'):
            raise serializers.ValidationError('email为必填项')
        return value

内容的提问来源于stack exchange，提问作者brainoverflow