poulpe/equipment/fields.py

from django.db import models
from django import forms


#class IdWidget(AdminMultipleChoiceFieldWidget):
class IdWidget(forms.widgets.CheckboxSelectMultiple):
    template_name = 'equipment/widgets/checkbox_select.html'
    option_template_name = 'equipment/widgets/checkbox_option.html'
    def __init__(self, *args, **kwargs):
        # nb_items = kwargs.pop('nb_items')
        # kwargs['choices'] = list(range(1, nb_items+1))
        super(IdWidget, self).__init__(*args, **kwargs)

    class Media:
        css = {
                'all': ('css/idwidget.css',)
                }

class IdFormField(forms.MultipleChoiceField):
    #widget = IdWidget

    def __init__(self, *args, **kwargs):
        if 'min_value' in kwargs:
            kwargs.pop('min_value')
        if 'max_value' in kwargs:
            kwargs.pop('max_value')
        super(IdFormField, self).__init__(*args, **kwargs)

class IdField(models.BigIntegerField):
    def parse_integer(self, n):
        res = []
        k = 1
        while(n > 0):
            if n & 1:
                res.append(k)
            n >>= 1
            k += 1
        return res

    def from_db_value(self, value, expression, connection, context):
        if value is None:
            return value
        return self.parse_integer(value)

    def to_python(self, value):
        if isinstance(value, list):
            return value

        if value is None:
            return value

        return self.parse_integer(value)

    def get_prep_value(self, value):
        res = 0
        for b in value:
            res |= 1 << (int(b)-1)
        return res

    def __init__(self, separator=",", *args, **kwargs):
        self.separator = separator
        super(IdField, self).__init__(*args, **kwargs)

    def deconstruct(self):
        name, path, args, kwargs = super(IdField, self).deconstruct()
        # Only include kwarg if it's not the default
        if self.separator != ",":
            kwargs['separator'] = self.separator
        return name, path, args, kwargs

    def formfield(self, **kwargs):
        # This is a fairly standard way to set up some defaults
        # while letting the caller override them.
        defaults = {'form_class': IdFormField}
        defaults.update(kwargs)
        return super(IdField, self).formfield(**defaults)