Django 创建自定义模型字段 [英] Django creating a custom model field

问题描述

我正在尝试在 Django 中创建一个自定义字段，它将采用十进制货币值(例如:1.56 英镑)并将其作为整数(例如:156)保存在数据库中以存储货币值.

这是我到目前为止所拥有的(我已经将固定值进行了测试)

class CurrencyField(models.DecimalField):__metaclass__ = models.SubfieldBasedef get_internal_type(self):返回'PositiveIntegerField'def to_python(self, value):打印CurrentField to_python"返回十进制(值)/100def get_db_prep_value(self, value, connection, Prepared=False):打印CurrentField get_db_prep_value"如果值为无:返回值打印类型(值)返回整数(值*100)

我正在关注 Python 1.7 文档以创建自定义模型字段.

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 方法工作正常(如果我在数据库中手动输入值，它将返回正确的十进制)，但是它永远不会保存正确的值.

我也尝试过使用 get_prep_value 并且结果相同.

如何让它保存正确的值?

解决方案

基于整数的 MoneyField

我已经使用这个 Django 代码段有一段时间了，但后来意识到它在保存数据库之前转换为整数时会引入浮点工件.

此外，从 Django 1.9 SubfieldBase 已被弃用，我们应该使用 Field.from_db_value 代替.所以我编辑了代码来解决这两个问题.

class CurrencyField(models.IntegerField):description = "一个在数据库中将美元保存为便士 (int) 的字段，但表现得像一个浮点数"def get_db_prep_value(self, value, *args, **kwargs):如果值为无:返回无返回 int(round(value * 100))def to_python(self, value):如果值为 None 或 isinstance(value, float):返回值尝试:返回浮点数(值)/100除了(类型错误，值错误):raise ValidationError("这个值必须是一个整数或者一个字符串代表一个整数.")def from_db_value(self, value, expression, connection, context):返回 self.to_python(value)def formfield(self, **kwargs):从 django.forms 导入 FloatField默认值 = {'form_class': FloatField}defaults.update(kwargs)返回 super(CurrencyField, self).formfield(**defaults)

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.

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)

I am following the Python 1.7 documentation for creating custom model fields.

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.

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

How can I make it save the correct value?

解决方案

Integer based MoneyField

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.

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)

这篇关于Django 创建自定义模型字段的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！