Modelform with reverse foreignkey

[Kiran]

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I am trying to create a ModelForm for movie Model from which it must be possible to select a number of theatre for each movie.Since theatre is reverse foreignkey i think ModelForm doesn't automatically  saves theatre values to the database.i tried to override the save method and ended up with the error.

Exception Type:
ValueError
Exception Value:
save() prohibited to prevent data loss due to unsaved related object 'movie'.

Anyone please help me to solve this and thanks in advance.

class movieAdminForm(forms.ModelForm):

    theatre = forms.ModelMultipleChoiceField(queryset=theatre.objects.all(),
                                             widget=forms.widgets.CheckboxSelectMultiple())
   

    class Meta:
        model = movie
        fields = ('image', 'image2', 'title', 'language', 'director', 'cast', 'y_tube_url',
                      'synopsis', 'like', 'music', 'cast',
                      'duration', 'genre', 'date', 'rating', 'writer','theatre')


    def save(self,*args,**kwargs):
        super(movieAdminForm,self).save(*args,**kwargs)
        self.instance.theatre.clear()
        for i in self.cleaned_data['theatre']:
            self.instance.theatre.add(i)