Django创建自定义模型字段

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我正在尝试在Django中创建一个自定义字段，该字段将使用十进制货币值（例如：1.56英镑）并将其保存为数据库中的整数（例如：156）来存储货币值。

I am trying to create a custom field in Django which will take a decimal currency value (example: £1.56) and save it in the database as an Integer (example: 156) to store currency values.

这是我到目前为止的结果（我已经测试了固定值）

This is what I have so far (I have put fixed values to test)

class CurrencyField(models.DecimalField): __metaclass__ = models.SubfieldBase def get_internal_type(self): return 'PositiveIntegerField' def to_python(self, value): print "CurrentField to_python" return Decimal(value)/100 def get_db_prep_value(self, value, connection, prepared=False): print "CurrentField get_db_prep_value" if value is None: return value print type(value) return int(value*100)

我正在关注用于创建自定义模型字段的Python 1.7文档。

在上面的代码中，当我使用此字段保存模型时，永远不会调用 get_db_prep_value 方法。 to_python 方法可以正常工作（如果我在数据库中手动输入值，它将返回正确的十进制数），但是它将永远不会保存正确的值。

In the above code, the get_db_prep_value method is never being called when I save the model using this field. The to_python method is working fine (if I manually enter the value in the DB it will return the correct decimal), however it will never save the correct value.

我也尝试过使用 get_prep_value ，并且结果相同。

I have also tried using get_prep_value and this has the same result.

如何使它保存正确的值？

How can I make it save the correct value?

推荐答案

基于整数的MoneyField

我已经使用了Django这段代码了一段时间，但后来意识到在保存数据库之前转换为整数时会引入浮点伪像。

I've been using this Django snippet for some time, but realized later it was introducing floating-point artifacts when converting to an integer before saving the the database.

此外，自Django 1.9起， SubfieldBase已弃用，我们应该改用Field.from_db_value。因此，我已经编辑了代码来解决这两个问题。

Also, as of Django 1.9 SubfieldBase has been deprecated and we should use Field.from_db_value instead. So I've edited the code to fix both of these issues.

class CurrencyField(models.IntegerField): description = "A field to save dollars as pennies (int) in db, but act like a float" def get_db_prep_value(self, value, *args, **kwargs): if value is None: return None return int(round(value * 100)) def to_python(self, value): if value is None or isinstance(value, float): return value try: return float(value) / 100 except (TypeError, ValueError): raise ValidationError("This value must be an integer or a string represents an integer.") def from_db_value(self, value, expression, connection, context): return self.to_python(value) def formfield(self, **kwargs): from django.forms import FloatField defaults = {'form_class': FloatField} defaults.update(kwargs) return super(CurrencyField, self).formfield(**defaults)