Ticket #422 (closed defect: invalid)

Opened 6 years ago

Last modified 5 years ago

Custom Field that defines an __init__ without arguments

Reported by: anonymous Owned by: andrew
Priority: major Milestone: 0.7.1
Component: commands Version: 0.7
Keywords: Cc:


I have a custom field that store the last modification time of the model in seconds since the Epoch.

This field defines a constructor without arguments, and all field configuration is set when the super class is called.

When I try to migrate the models using this field, I have an error :

  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/South-0.7-py2.5.egg/south/orm.py", line 237, in eval_in_context
    return eval(code, globals(), fake_locals)
  File "<string>", line 1, in <module>
TypeError: __init__() got an unexpected keyword argument 'default'

Here is the custom field definition:

class VersionField(models.IntegerField):
    def __init__(self):
        models.IntegerField.__init__(self, blank=False, default=0)
    def pre_save(self, model_instance, add):
        value = int(math.floor(time.time()))
        setattr(model_instance, self.attname, value)
        return value

And I tried these two ways to declare the field:

add_introspection_rules([], ['^foo\.%s' % VersionField.__name__, ])
add_introspection_rules([([VersionField, ], [], {}, ), ], ['^foo\.%s' % VersionField.__name__, ])

Should I add an *args, kwargs to the constructor event if they are not used to make it work ?


Change History

comment:1 Changed 6 years ago by andrew

  • Status changed from new to closed
  • Resolution set to invalid
  • Milestone set to 0.7.1

Ah, yes, I see the problem. You'll need to write new introspection rules that _remove_ the keyword arguments, as your field has inherited some from Field.

The ignore_if option excludes the field from the frozen version if the attribute it's pointing to coerces to true, so a rule like this would be enough to stop it putting default in:

"default": ["default", {"ignore_if": "name"}]

(This works because fields always have a name).

Also, in future, I'd appreciate it if individual help went to the mailing list - it's kind of hard to categorise it here into a bug or feature request!

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