extra_kwargsをアクションごとに変更する方法

Django Rest FrameworkでREST APIを作っているのですが、CommandSerializer内でModelViewSetのアクション（POST, PATCH）に応じてextra_kwargsを動的に変更する方法がわかりません。
どうすればできるかおしえてください！

python
1#こんな感じでやりたい！
2
3#post
4if self.action == 'create':
5    extra_kwargs = {
6        'response': {'required': False}
7    }
8#patch
9elif self.action == 'partial_update':
10    extra_kwargs = {
11         'response': {'required': True}
12    }

python
1#シリアライザ
2class CommandSerializer(serializers.ModelSerializer):
3
4    upfile = UpFileSerializer(read_only=True)
5    downfile = DownFileSerializer(read_only=True)
6
7    class Meta:
8        model = Command
9        fields = '__all__'
10        extra_kwargs = {
11            'response': {'required': False}
12        }
13
14    
15    def create(self, validated_data):
16        c = Command(
17            sender=validated_data['sender'], 
18            cmd=validated_data['cmd'], 
19            recipient=validated_data['recipient']
20        )
21        c.finished('cmd')
22        return c
23
24    def update(self, instance, validated_data):
25        instance.response = validated_data.get('response', instance.response)
26        instance.finished('resp')
27        return instance

python
1#モデル
2class Command(models.Model):
3    sender = models.IntegerField()
4    cmd = models.TextField()
5    recipient = models.TextField()
6    response = models.TextField()
7    upfile = models.OneToOneField(UpFile, default=None, null=True, blank=True, unique=True, related_name='command', on_delete=models.CASCADE)
8    downfile = models.OneToOneField(DownFile, default=None, null=True, blank=True, unique=True, related_name='command', on_delete=models.CASCADE)
9    cmd_finished = models.DateTimeField(null=True, blank=True)
10    resp_finished = models.DateTimeField(null=True, blank=True)
11
12    def finished(self, op):
13        if op == 'cmd':
14            self.cmd_finished = timezone.now()
15        elif op == 'resp':
16            self.resp_finished = timezone.now()
17        self.save()
18
19    def connect_upfile(self, qs):
20        self.upfile = qs
21        self.save()
22
23    def connect_downfile(self, qs):
24        self.downfile = qs
25        self.save()

行動規範の内容に同意します

回答1件

自己解決

python
1class CommandUpdateSerializer(CommandSerializer):
2
3    class Meta:
4        model = Command
5        fields = '__all__'
6        extra_kwargs = {
7            'id': {'read_only': True},
8            'sender': {'read_only': True},
9            'cmd': {'read_only': True},
10            'recipient': {'read_only': True},
11            'cmd_finished': {'read_only': True},
12            'response': {'required': True}
13        }