class UsersSerializer(serializers.ModelSerializer):
    password = serializers.CharField(write_only=True)
    gender = serializers.SerializerMethodField()
    date_of_birthday = serializers.SerializerMethodField()

    class Meta:
        model = User
        fields = ('id',  'phone', 'first_name', 'last_name', 'is_active',
                  'avatar', 'password', 'gender', 'date_of_birthday', )
        write_only_fields = ('password', )
        read_only_fields = ('is_staff', 'is_active', 'date_joined', )

    def get_gender(self, obj):
        try:
            gender = obj.client.get().gender or None
        except Client.DoesNotExist:
            return None
        return gender

    def get_date_of_birthday(self, obj):
        try:
            date_of_birthday = obj.client.get().date_of_birthday or None
        except Client.DoesNotExist:
            return None
        return date_of_birthday

    def create(self, validated_data):
        user = super(UsersSerializer, self).create(validated_data)
        user.set_password(validated_data['password'])
        user.save()

        return user

    def update(self, instance, validated_data):
        gender = self.context.get('request').data.get('gender', None)
        date_of_birthday = self.context.get('request').data.get('date_of_birthday', None)

        if gender or date_of_birthday:
            kwargs = {}
            if gender:
                kwargs.update({
                    'gender': gender
                })
            if date_of_birthday:
                date_of_birthday = datetime.strptime(date_of_birthday, "%Y-%m-%d")
                kwargs.update({
                    'date_of_birthday': date_of_birthday.date()
                })
            kwargs.update({
                'user': instance
            })
            client, created = Client.objects.get_or_create(user=instance)
            client.date_of_birthday = kwargs.get('date_of_birthday', None)
            client.gender = kwargs.get('gender', None)
            client.save()
        instance.save()
        return instance