Django：知道属性是否为默认值 [英] Django : Know if property is the default value

问题描述

如何知道值是模型属性的默认值。

How can you know if a value is the default value for a Model's property.

例如

class Alias(models.Model) :
  image = models.ImageField(upload_to='alias', default='/media/alias-default.png')

a = Alias.get("123")
# this doesn't work
if a.image == a.image.default :
  pass
# nor this
if a.image == Alias.image.default :
  pass

我尝试挖掘文档，但没有看到任何东西。 >

I tried digging in the docs, but didn't see anything.

推荐答案

Django中的默认值与SQL默认值不同 - 管理员自动填写新对象创建的表单域。

The default in Django is not the same as SQL default - it's there merely for admin to auto-fill the form field on new object creation.

如果要比较某些值定义为默认值你必须在别的地方定义它（即在 settings.py ）。喜欢：

If you want to compare something to value defined as default you have to define it somewhere else (i.e. in settings.py). Like:

class MyModel(models.Model):
    ...
    my_field = models.IntegerField(default=settings.INT_DEFAULT)

默认值 value存储在 MyModel._meta._fields（）[field_creation_index] .default 中，但请注意，这是在内部挖掘。

The default value is stored in MyModel._meta._fields()[field_creation_index].default but be aware that this is digging in internals.

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