Django：为什么这个自定义模型字段的行为不如预期的那样？ [英] Django: Why does this custom model field not behave as expected?

问题描述

以下字段意味着将货币格式化为二进制十进制（量化）。您可以看到它返回存储小数的< decimal> .quantize（TWOPLACES）版本。然而，当我在Django管理员中查看这个时，它不会这样做。如果我将 50 放在使用 CurrencyField（）的字段中，并在管理员中查看， code> 50 vs 50.00 。为什么是这样？

The following field is meant to format money as a two places decimal (quantized). You can see that it returns a <decimal>.quantize(TWOPLACES) version of the stored decimal. When I view this in the Django admin however, it doesn't do that. If I put in 50 to a field that is using CurrencyField() and view it in the admin, I get 50 vs 50.00. Why is that?

from django.db import models
from decimal import Decimal


class CurrencyField(models.DecimalField):
    """
    Only changes output into a quantized format. Everything else is the same.
    """
    def __init__(self, *args, **kwargs):
        kwargs['max_digits'] =  8
        kwargs['decimal_places'] = 2
        super(CurrencyField, self).__init__(*args, **kwargs)

    def to_python(self, value):
        try:
            return super(CurrencyField, self).to_python(value).quantize(Decimal('0.01'))
        except AttributeError:
            return None

更新：我试着把 return'Hello World'代替 return super（CurrencyField，self）.to_python（value）.quantize（Decimal （'0.01'）），甚至没有在shell中显示Hello World。它再次出现 50 。这是否意味着当我访问一个模型的属性是一个 CurrencyField（）时，它不会调用 to_python（）？

Update: I tried putting return 'Hello World' in place of return super(CurrencyField, self).to_python(value).quantize(Decimal('0.01')) and it didn't even show 'Hello World' in the shell. It put out 50 again. Does this mean that when I access an attribute of a model that is a CurrencyField() it doesn't call to_python()?

推荐答案

也许您可以尝试将其添加到您的字段中：

Maybe you could try adding this to your field:

__metaclass__ = models.SubfieldBase

另见 here 。

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