filter choices for many to many field in modelform django

Question

i want to filter the many to many field in modelform.

class IdealBehaviour(models.Model):
    cbs_role = models.ManyToManyField(CbsRole, null=True, blank=True)
    cbs = models.ForeignKey('cbs.CBS', null=True, blank=True)
    ideal_behaviour = models.CharField(max_length=500, null=True, blank=True)
    Description = models.CharField(max_length=1000, null=True, blank=True)
    created_time = models.DateTimeField(auto_now_add = True,null=True, blank=True)

class StandardWork(models.Model):
    cbs_and_role = models.ManyToManyField('userdata.CbsRole', null=True, blank=True)
    standard_work_number = models.BigIntegerField(null=True, blank=True)
    system_name= models.CharField(max_length=500, null=True, blank=True)
    system_description=models.TextField(null=True, blank=True)
    ideal_behaviour = models.ManyToManyField ('userdata.IdealBehaviour', null=True, blank=True)
    publish = models.BooleanField(default=False)
    created_time = models.DateTimeField(auto_now_add = True,null=True, blank=True)

class TodoListForm(ModelForm):  # used in manage view
    class Meta:
        model = StandardWork
        exclude = ('publish', 'cbs_and_role', 'standard_work_number')
        widgets = {
              'system_description': forms.Textarea(attrs={'rows':3}),
            } 

i want to display the choices of ideal_behaviour for the query

cbsobject = CBS.objects.get(id=dat)
idealbehaviour = IdealBehaviour.objects.filter(cbs=cbsobject)

I want to choices for ideal_behaviour in TodoListForm as idealbehaviour only.

How can i query to display ideal-behaviour assosciated with that perticuler cbs only in modelform?

i got the solution

def __init__(self, *args, **kwargs):
        super(PollForm, self).__init__(*args, **kwargs)
        if self.instance:
            print "printing in form"
            print self.instance.id
            self.fields['ideal_behaviour'].queryset = IdealBehaviour.objects.filter(cbs__exact=self.instance.id)

but i dont how to get the id for cbs. self.instance.id its giving for standardwork id. i want id for cbs. ie cbsobject i want in form as a instance. after that its working fine.

Answer 1

Got the solution. i don't know its feasible or not but i put the forms in views file only so i can get the instance for cbsobject.

class PollForm(forms.ModelForm): # used in manage view
                    class Meta:
                        model = StandardWork
                        exclude = ('cbs_and_role','publish', 'standard_work_number')
                        widgets = {
                          'system_description': forms.Textarea(attrs={'rows':3}),
                        } 
                    def __init__(self, *args, **kwargs):
                        super(PollForm, self).__init__(*args, **kwargs)
                        if self.instance:
                            print "printing in form"
                            print self.instance.id
                            self.fields['ideal_behaviour'].queryset = IdealBehaviour.objects.filter(cbs__exact=cbsobject)

if there any better solution then please let me know. And please guide me in which term this approch is not good. Thank you.