I often found this handy too. Here's my implementation on bitbucket[1].
There are tests[2] and documentation[3]. It's something I wanted propose to
Django core as well but never found time to do so. :)
In my implementation I chose to assign numeric values explicitly:
SetField(choices=((1,"pizza"),(2,"pasta"),(4,"seafood")))
instead of:
SetField(choices=("pizza","pasta","seafood"))
This is for two reasons:
1) It makes it compatible with Django's standard implementation of choices.
2) Implicit index assignment is bug prone if the order of choices changes.
[1] http://goo.gl/16t2h7
[2] http://goo.gl/C75KTq
[3] http://goo.gl/cs0J1U
On Fri, Nov 1, 2013 at 6:24 PM, Russell Keith-Magee <[email protected]
> wrote:
>
> Agreed - if we were going to implement this, we'd use a bit string
> implementation, not push it into a char field.
>
> Yours,
> Russ Magee %-)
>
>
> On Sat, Nov 2, 2013 at 4:22 AM, Michael Manfre <[email protected]> wrote:
>
>> Storing bits as a string is not an efficient use of space and is slower
>> to query. Any reason why you are not using the bit datatype with a length?
>> E.g. 'bit(%s)' % len(self.flags)
>>
>> Regards,
>> Michael Manfre
>>
>>
>> On Fri, Nov 1, 2013 at 3:50 PM, Paul Kenjora <[email protected]> wrote:
>>
>>> Hi,
>>>
>>> I'd like to propose a new field type I've used on several projects.
>>> Its a list of boolean flags all in one field. It replaces the need for
>>> many Boolean fields and has the same basic DB lookup capabilities. This is
>>> fully Admin compatible and Database agnostic.
>>>
>>> Here is the full code, I'm sure it could use some minor tweaks.
>>>
>>> from django.db import models
>>> from django.forms import MultipleChoiceField, CheckboxSelectMultiple
>>>
>>> class FlagField(models.Field):
>>>
>>> description = "A set of flags."
>>> __metaclass__ = models.SubfieldBase
>>>
>>> def __init__(self, flags, *args, **kwargs):
>>> self.flags = flags
>>> super(FlagField, self).__init__(*args, **kwargs)
>>>
>>> def db_type(self, connection):
>>> return 'char(%s)' % len(self.flags)
>>>
>>> def to_python(self, value):
>>> if isinstance(value, list) or isinstance(value, set):
>>> flagged = set(value)
>>> else:
>>> flagged = set()
>>> for i,c in enumerate(value):
>>> if c == '1' and i < len(self.flags): flagged.add(self.flags[i])
>>> return flagged
>>>
>>> def get_db_prep_value(self, value, connection, prepared=False):
>>> return ''.join(map(lambda flag: '1' if flag in value else '0',
>>> self.flags))
>>>
>>> def formfield(self, **kwargs):
>>> defaults = {'form_class': MultipleChoiceField,
>>> 'widget':CheckboxSelectMultiple, 'choices':map(lambda f: (f, f),
>>> self.flags)}
>>> defaults.update(kwargs)
>>> return super(FlagField, self).formfield(**defaults)
>>>
>>> Regards,
>>>
>>>
>>> --
>>> - Paul Kenjora
>>> - 602-214-7285
>>>
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