django - 非常简单的 Django 自定义字段

Question

我正在尝试做一个非常简单的自定义字段，但似乎无法让它工作。

目前，我将此字段添加到我的应用程序中的几乎所有模型中。我想将其指定为自定义字段以避免重复代码。

identifier = models.CharField(
    max_length = 20, 
    unique = True, validators = [validators.validate_slug],
    help_text = "Help text goes here."
)

我有的是这个:

class MyIdentifierField(models.CharField):

    description = "random string goes here"

    __metaclass__ = models.SubfieldBase

    def __init__(self, *args, **kwargs):
        kwargs['max_length'] = 20
        kwargs['unique'] = True
        kwargs['validators'] = [validators.validate_slug]
        kwargs['help_text'] = "custom help text goes here"
        super(MyIdentifierField, self).__init__(*args, **kwargs)

    def db_type(self, connection):
        return 'char(25)'

这样我就可以这样使用它:

identifier = MyIdentifierField()

但是，当我这样做时 python manage.py schemamigration --auto <myapp> ，我收到以下错误:

 ! Cannot freeze field 'geral.seccao.identifier'
 ! (this field has class geral.models.MyIdentifierField)

 ! South cannot introspect some fields; this is probably because they are custom
 ! fields. If they worked in 0.6 or below, this is because we have removed the
 ! models parser (it often broke things).
 ! To fix this, read http://south.aeracode.org/wiki/MyFieldsDontWork

我浏览了推荐的网页，但似乎仍然找不到解决方法。任何帮助表示赞赏。谢谢。

Answer 1

在描述你的领域时，你需要帮助 South 一点。有两种方法可以做到这一点，如文档所述:http://south.aeracode.org/wiki/MyFieldsDontWork

我的首选方法是在字段类上添加一个 South 字段三元组:

def south_field_triple(self):
    try:
        from south.modelsinspector import introspector
        cls_name = '{0}.{1}'.format(
            self.__class__.__module__,
            self.__class__.__name__)
        args, kwargs = introspector(self)
        return cls_name, args, kwargs
    except ImportError:
        pass

希望能帮到你。