#30857: When subclassing a model field, `max_length` cannot be passed as an
argument to `self.__init__`
-------------------------------------+-------------------------------------
Reporter: Robin (Robert) | Owner: nobody
Thomas |
Type: Uncategorized | Status: new
Component: Uncategorized | Version: 2.2
Severity: Normal | Resolution:
Keywords: models fields | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Description changed by Robin (Robert) Thomas:
Old description:
> {{{
> class MyCustomField(models.CharField):
> def __init__(self, *args, **kwargs):
> super().__init__(max_length=60, *args, **kwargs)
>
> class MyModel(models.Model)
> address_state = MyCustomField()
> }}}
>
> On attempting to migrate, I get:
>
> {{{
> super().__init__(max_length=60, *args, **kwargs)
> TypeError: __init__() got multiple values for keyword argument
> 'max_length'
> }}}
>
> Using `kwargs[max_length]` works just fine. However, the documentation
> says that `max_length` should be able to be passed to
> `super().__init__()` as an argument:
>
> https://docs.djangoproject.com/en/2.2/howto/custom-model-
> fields/#writing-a-field-subclass
>
> Either the documentation is incorrect and should be fixed, or this is a
> bug.
New description:
{{{
class MyCustomField(models.CharField):
def __init__(self, *args, **kwargs):
super().__init__(max_length=60, *args, **kwargs)
class MyModel(models.Model)
address_state = MyCustomField()
}}}
On attempting to migrate, I get:
{{{
super().__init__(max_length=60, *args, **kwargs)
TypeError: __init__() got multiple values for keyword argument
'max_length'
}}}
Using `kwargs[max_length]` works just fine. However, the documentation
says that `max_length` should be able to be passed to `super().__init__()`
as an argument:
https://docs.djangoproject.com/en/2.2/howto/custom-model-fields/#writing-a
-field-subclass
Either the documentation is incorrect, or this is a bug.
--
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Ticket URL: <https://code.djangoproject.com/ticket/30857#comment:1>
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