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djangodjango-ormdjango-managers

Custom managers in a Many-to-Many relation for usual filters

class Proposal(models.Model):
    author = models.ForeignKey(Person, related_name="author")

    def get_tags(self):
        return Tag.objects.filter(tagged_proposals=self.id) 

class Tag(models.Model):
    tagged_proposals = models.ManyToManyField(Proposal)
    name = models.CharField(primary_key=True, max_length=60)

I need to list the proposal's tags on a certain template so I would write {% for tag in proposal.get_tags %} and it works perfectly.

Now I read about Managers and it seems a good move to convert my get_tags into a Manager. I tried the following but it didn't output a thing. What am I doing wrong? Does it make sense to turn it a Manager in the first place?

class ProposalsTagsManager(models.Manager):
    def get_query_set(self):
                proposal_id = how-do-i-get-the-proposal-id???
        return Tag.objects.filter(tagged_proposals=proposal_id)

usage: {% for tag in p.tags.all %} output: nothing

Solution

  • You don't need a custom function for this.

    When a table is being referenced with a ManyToManyField you get a method called MODEL_set to get a queryset of that model.

    So in your case you can reference all your tags like this:

    proposal = Proposal.objects.get(pk=1)
tags = proposal.tag_set.all() # You can also use filter here