django manytomany and the modelform

Question

I am really new to django, and I have some questions about how django's M2M works and also how it works with the modelForm or the forms.Form am currently working on an application that contains the following models:

class Agent(models.Model):
    user = models.ForeignKey(User)
    assigned_by = models.ForeignKey('self')
    date = models.DateField(auto_now_add=True)

    def __str__(self):
        return str(self.user)

class Region(models.Model):
    name = models.CharField(max_length=50)


# Agent to Region many-to-many
class ARM2M(models.Model):
    agent = models.ForeignKey(Agent)
    region = models.ForeignKey(Region)
    is_manager = models.BooleanField(default=False)

Constraints: an agent can be in multiple regions, and he/she can be one of the managers in any of those regions that he/she is in.

Question#1: is there a way to present such logic with the many-to-many feature in django model?

-end-of-question#1-

So I have this AgentForm for an agent manager to add an new agent in his/her regions. But I know this form is not working: because in the MultipleChoiceField, I have no way to get the current loggedin agent, to present the available regions. In other words, I am stuck.

class AgentForm(forms.Form):
    agent = forms.IntegerField(widget=forms.HiddenInput()) 
    regions = forms.MultipleChoiceField(choices=RAM2M.objects.filter(agent=agent, is_manager=True))

    def save(self):
        agent_id = self.cleaned_data['assigned_by']
        agent = Agent.objects.get(pk=int(agent_id))
        self.instance.assigned_by = agent
        super(AgentForm, self).save()

    class Meta:
        model=Agent
        exclude = ('assigned_by')

Question#2: How do I construct a form for an existing agent to add a new agent to the regions where he/she is a manager.

Thanks,

Maxim

score 0 · Accepted Answer · edited May 23 '17 at 11:55

Question #1: you can specify an intermediate model for the M2M relationship using the through argument:

class Agent(models.Model):
    ...
    regions = models.ManyToManyField(Region, through='ARM2M')

(See http://docs.djangoproject.com/en/dev/topics/db/models/#intermediary-manytomany)

Regarding question #2, if think that this has the answer you're looking for: Creating a dynamic choice field

django manytomany and the modelform

1 Answers1