Django Rest Framework: serializing/deserializing 一个计算字段

Question

我刚开始使用 Django 和 Django REST 框架。我有以下型号：

class Account(models.Model):
    name = models.CharField(max_length=100, blank=False)
    vat_perc = models.DecimalField(max_digits=4, decimal_places=2)
    def __str__(self):
        return "ACCOUNT: {0} -- {1}".format(self.name, str(self.vat_perc))


class Entry(models.Model):
    account = models.ForeignKey(Account)
    description = models.CharField(max_length=100)
    taxable_income = models.DecimalField(max_digits=10, decimal_places=2)
    total_amount = models.DecimalField(max_digits=10, decimal_places=2, null=True)

    def save(self, *args, **kwargs):
        selected_vat = Account.objects.get(pk=self.account).vat_perc
        self.total_amount = self.taxable_income * (100.00+selected_vat)/100.00
        super(Entry, self).save(*args, **kwargs)

我们的想法是读取用户刚刚选择的 account 记录中的 vat_perc 值，然后执行计算以确定 total_amount 值，然后将其保存在数据库的 entry 记录中（我知道由于数据库中的数据重复，有些人会认为这是次优的；无论如何请关注我）。

total_amount 字段应在请求时定期序列化。相反，序列化程序不应该为反序列化做任何事情，因为模型中 save 方法的覆盖会在创建或修改发生时负责更新值。如果我正确地获得了文档，这意味着将序列化器 class 中的 total_amount 字段设置为 read_only.

现在，这些是我的序列化程序：

class AccountSerializer(serializers.ModelSerializer):
    class Meta:
        model = Account
        fields = ('id', 'name', 'vat_perc',)


class EntrySerializer(serializers.ModelSerializer):
    class Meta:
        model = Entry
        fields = ('id', 'account', 'description', 'taxable_income', 'total_amount',)

    total_amount = serializers.ReadOnlyField()
    # alternatively: total_amount = serializers.FloatField(read_only=True)

但这是我得到的错误：

Got a TypeError when calling Entry.objects.create(). This may be because you have a writable field on the serializer class that is not a valid argument to Entry.objects.create(). You may need to make the field read-only, or override the EntrySerializer.create() method to handle this correctly. Original exception text was: int() argument must be a string, a bytes-like object or a number, not 'Account'.

最后一句话对我来说特别难懂。我弄错了什么吗？有什么提示吗？提前致谢。

Answer 1

感谢Claudiu。在序列化程序中使用 SlugRelatedField class 和 decimal.Decimaltype 而不是 float ，因为我犯了错误。以下代码现在有效：

class Account(models.Model):
    name = models.CharField(max_length=100, blank=False)
    vat_perc = models.DecimalField(max_digits=4, decimal_places=2)
    def __str__(self):
        return "ACCOUNT: {0} -- {1}".format(self.name, str(self.vat_perc))


class Entry(models.Model):
    account = models.ForeignKey(Account)
    description = models.CharField(max_length=100)
    taxable_income = models.DecimalField(max_digits=10, decimal_places=2)
    total_amount = models.DecimalField(max_digits=10, decimal_places=2, null=True)

    def save(self, *args, **kwargs):
        self.total_amount = self.taxable_income * (decimal.Decimal(100.00) + self.account.vat_perc) / decimal.Decimal(100.00)
        super(Entry, self).save(*args, **kwargs)

serializers.py

class AccountSerializer(serializers.ModelSerializer):
    class Meta:
         model = Account
         fields = ('id', 'name', 'vat_perc',)


class EntrySerializer(serializers.ModelSerializer):
    class Meta:
        model = Entry
        fields = ('id', 'account', 'description', 'taxable_income', 'total_amount',)

    total_amount = serializers.ReadOnlyField()
    account = serializers.SlugRelatedField(queryset=Account.objects.all(), slug_field="vat_perc")

Django Rest Framework: serializing/deserializing 一个计算字段

Django Rest Framework: serializing/deserializing a calculated field

django

django-rest-framework