Django-filter 2 use @property to filter?

user_6953017 0
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I've got this filter:

class SchoolFilter(django_filters.FilterSet):
    class Meta:
        model = School
        fields = {
            'name': ['icontains'],
            'special_id': ['icontains'],
        }

Where special_id is a @property of the School Model:

@property
    def special_id(self):
        type = self.type
        unique_id = self.unique_id
        code = self.code
        if unique_id < 10:
            unique_id = f'0{unique_id}'
        if int(self.code) < 10:
            code = f'0{self.code}'
        special_id = f'{code}{type}{id}'
        return special_id

I've tried to google some answers, but couldn't find anything. Right now If I use my filter like I do I only receive this error:

'Meta.fields' contains fields that are not defined on this FilterSet: special_id

How could I define the property as a field for this FilterSet? Is it even possible for me to use django-filter with a @property?

Thanks for any answer!

Update:

Figured it out. Not the prettiest solution, but ayyy

class SchoolFilter(django_filters.FilterSet):
    special_id = django_filters.CharFilter(field_name="special_id", method="special_id_filter", label="Special School ID")

    def special_id_filter(self, queryset, name, value):
        schools_pk = []
        for obj in queryset:
            if obj.special_id == value:
                schools_pk.append(obj.pk)
        queryset = queryset.filter(pk__in=schools_pk)
        return queryset

    class Meta:
        model = School
        fields = {
            'name': ['icontains'],
            'special_id': ['icontains'],
        }
django-filter django python
2 Answers

You can't. FilterSet will only filter on actual fields, since FilterSet alters a QuerySet.

QuerySets do a database call based on the filters applied, which means you can only filter on fields actually stored in the database.

You could annotate your QuerySet to add the special_id, but an annotation like this is pretty complex to chain together.

A better way to do this would be to create a custom filter on your FilterSet, but I'm not exactly sure how to do this. If you can explain what special_id is, and exactly why you want to search it through icontains, then I could maybe point you in the right direction.

This is an implementation of a MethodFilter, which I think is similar what you want.

user_15668990

FilterSet operates by filtering queryset (adding where conditions to the underlying sql). Which means, FilterSet can operate only on Columns that are present in the database. Here the special_id is a computed property (It is not a column, it is calculated on the fly using other fields/columns), So it wont work.

The work around is to make special_id a normal field/column, compute the value at runtime and write to database at the time of save.

user_27179820
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