How can I sort a list of models considering one element of a many-to-many relation?

Question

We're building an API using Django Rest Framework where I have the following schema:

    class Main(models.Model):
        name = models.CharField(default=None, max_length=200, blank=True, null=True)
        # [...]
    
    
    class Attribute(models.Model):
        main = models.ForeignKey('Main', on_delete=models.CASCADE, related_name='attrs')
        code = models.CharField(max_length=50, null=True)
        value = models.CharField(max_length=50, null=True)

I want to build a queryset (paginated) for a list of Main objects and I would like to sort them using the "value" of certain Attribute "code".

For example, if we suppose three attributes are: "age" (8-18), "grade" ("A", "B", "C", etc.), "stars" (0-5) and Main were "students" I would like to be able to build a queryset for the list of students ordered by "age" and "grade" values.

I've tried something like:

queryset = Main.objects.filter(id__in=ids).filter(attrs__code='age').order_by('attrs_value')

Edited: Yes, actually this solution worked, but how can I deal with numeric order? I mean, "12.22" should be after "3.2".

Extra: Would I be able to reach a multiple attr order?

score 1 · Accepted Answer · answered Jul 27 '20 at 11:41

1

Have you tried this:

queryset = Main.objects.filter(id__in=ids).filter(attrs__code='age').order_by('attrs__value')

answered Jul 27 '20 at 11:41

Pruthvi Barot

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14

Missing \' was a typo. Actually, this works, but I'm having two problems: dealing with numeric order (against text order) and multiple ordering – rodrigobb Jul 27 '20 at 12:54
Do you want to order_by multiple values of attrs? – Pruthvi Barot Jul 27 '20 at 12:57
because order_by does on fields, not field_values – Pruthvi Barot Jul 27 '20 at 12:58
And you can order by numeric values if know there is a numeric or char value. like this https://stackoverflow.com/a/2969983/12261752 – Pruthvi Barot Jul 27 '20 at 13:02
Selected this answer as it right for the initial question and close for the extras – rodrigobb Jul 28 '20 at 09:32

How can I sort a list of models considering one element of a many-to-many relation?

1 Answers1