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94 lines
3.4 KiB
Python
94 lines
3.4 KiB
Python
import django_filters
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import itertools
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from django import forms
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from django.db.models import Q
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from django.utils.encoding import force_text
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class NullableModelMultipleChoiceField(forms.ModelMultipleChoiceField):
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"""
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This field operates like a normal ModelMultipleChoiceField except that it allows for one additional choice which is
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used to represent a value of Null. This is accomplished by creating a new iterator which first yields the null
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choice before entering the queryset iterator, and by ignoring the null choice during cleaning. The effect is similar
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to defining a MultipleChoiceField with:
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choices = [(0, 'None')] + [(x.id, x) for x in Foo.objects.all()]
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However, the above approach forces immediate evaluation of the queryset, which can cause issues when calculating
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database migrations.
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"""
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iterator = forms.models.ModelChoiceIterator
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def __init__(self, null_value=0, null_label='None', *args, **kwargs):
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self.null_value = null_value
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self.null_label = null_label
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super(NullableModelMultipleChoiceField, self).__init__(*args, **kwargs)
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def _get_choices(self):
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if hasattr(self, '_choices'):
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return self._choices
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# Prepend the null choice to the queryset iterator
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return itertools.chain(
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[(self.null_value, self.null_label)],
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self.iterator(self),
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)
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choices = property(_get_choices, forms.ChoiceField._set_choices)
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def clean(self, value):
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# Strip all instances of the null value before cleaning
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if value is not None:
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stripped_value = [x for x in value if x != force_text(self.null_value)]
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else:
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stripped_value = value
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super(NullableModelMultipleChoiceField, self).clean(stripped_value)
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return value
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class NullableModelMultipleChoiceFilter(django_filters.ModelMultipleChoiceFilter):
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"""
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This class extends ModelMultipleChoiceFilter to accept an additional value which implies "is null". The default
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queryset filter argument is:
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.filter(fieldname=value)
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When filtering by the value representing "is null" ('0' by default) the argument is modified to:
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.filter(fieldname__isnull=True)
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"""
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field_class = NullableModelMultipleChoiceField
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def __init__(self, *args, **kwargs):
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self.null_value = kwargs.get('null_value', 0)
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super(NullableModelMultipleChoiceFilter, self).__init__(*args, **kwargs)
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def filter(self, qs, value):
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value = value or () # Make sure we have an iterable
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if self.is_noop(qs, value):
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return qs
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# Even though not a noop, no point filtering if empty
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if not value:
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return qs
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q = Q()
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for v in set(value):
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# Filtering by "is null"
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if v == force_text(self.null_value):
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arg = {'{}__isnull'.format(self.name): True}
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# Filtering by a related field (e.g. slug)
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elif self.field.to_field_name is not None:
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arg = {'{}__{}'.format(self.name, self.field.to_field_name): v}
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# Filtering by primary key (default)
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else:
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arg = {self.name: v}
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if self.conjoined:
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qs = self.get_method(qs)(**arg)
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else:
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q |= Q(**arg)
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if self.distinct:
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return self.get_method(qs)(q).distinct()
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return self.get_method(qs)(q)
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