Django - 具有伴随存储字段的自定义虚拟模型字段 [英] Django - Custom virtual model field with companion stored field

问题描述

我想要一个 ConfirmationField 字段类型。我希望这个字段像布尔字段一样工作。我不需要将这些信息存储在数据库中，而是我想在单独的字段中存储确认日期。

I would like to have a ConfirmationField field type. I want this field to work like a boolean field. I don't need to store this information on database instead I would like to store the date of confirmation on a seperate field.

class MyModel(models.Model):
    confirmation = ConfirmationField()


m = MyModel()
m.confirmation # False
m.confirmation_timestamp # None

m.confirmation = True
m.save()

m.confirmation_timestamp # datetime object


m.confirmation = False
m.save()

m.confirmation_timestamp # None again

我需要将这两个字段作为 Field 实例，我需要能够在Admin中使用它们。

I need to have both fields as Field instances, I need to be able to use them in Admin for example.

我已阅读文档并检查代码， ForeignKey 使用以下代码更改其数据库列名：

I have read the docs and checked the code, ForeignKey changes its database column name with the following code:

def get_attname(self):
    return '%s_id' % self.name

但是，我无法弄清楚我如何使用其余的的代码为例。似乎我的目标不需要太多的复杂性。

But I couldn't figure out exacly how I can use the rest of the code as an example. It seems my goal doesn't require tto much complexity.

我还发现 ImageField 保存额外的信息，当模型被保存：

I have also found ImageField saved extra information when the model is saved:

    if self.field.width_field:
        setattr(self.instance, self.field.width_field, self.width)
    if self.field.height_field:
        setattr(self.instance, self.field.height_field, self.height)

但当然，我不希望将确认本身存储在数据库中。因为（ confirmation_timestamp - > 确认）无 == False 和< datetime instance> == True

But of course I don't want confirmation itself to be stored in the database. I would cause redundancy since (confirmation_timestamp -> confirmation) None==False and <datetime instance>==True.

任何指针/想法都不胜感激。

Any pointers/ideas are appreciated.

谢谢。

编辑：目前看来，这是不可能的。我最终改变了我的API这是一个snipplet，给出一个想法，我是如何做到的：

edit: It appears this is not currently possible. I have ended up changing my API. Here is a snipplet to give an idea how I did it:

    value = {'BooleanField': True,
             'DateTimeField': datetime.datetime.now(),
             'DateField': datetime.date.today(),
             'IntegerField': 1,
            }[instance._meta.get_field(field_name).get_internal_type()]
    setattr(instance, field_name, value)

具有上述任何类型的确认字段，并设置正确的值。并且可以使用 bool（getattr（instance，field_name）。

You can have a confirmation field any type mentioned above and it sets the correct value. And confirmation checking can be done with bool(getattr(instance, field_name).

推荐答案

如果我有这个权利，请考虑：

if I got this right, consider:

class Modelname(models.Model):
    """(Modelname description)"""

    confirmation_timestamp = models.DateTimeField(blank=True)

    def _set_confirmation(self, value):
        if not value:
            self.confirmation_timestamp = None
        else:
            self.confirmation_timestamp = datetime.datetime.now()

    def _get_confirmation(self):
        return bool(self.confirmation_timestamp)

    confirmation = property(_get_confirmation, _set_confirmation)
    confirmation.short_description = "Confirmation"
    confirmation.boolean = True # have it nicely displayed in admin

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