Question

I am using jquery chosen. I’ve added null=True and blank=True on ManyToMany and ForeignKey. But then why I am getting validation error on ManyToManyField in template? I tried to submit the form without filling the ManyToManyField and ForeignKey in admin and it works but not in tempalte. Will you please help? thanks

ManyToManyError – Enter a list of values.

Model

class Movie(models.Model):
    title = models.CharField(max_length=100)
    slug = models.SlugField(unique=True, max_length=100)
    director = models.ManyToManyField(Director, null=True, blank=True)
    writer = models.ManyToManyField(Writer, null=True, blank=True)
    producer = models.ManyToManyField(Producer, null=True, blank=True)
    starring = models.ManyToManyField(Starring, null=True, blank=True)
    screenplay = models.ManyToManyField(Screenplay, null=True, blank=True)

    editing = models.ForeignKey(Editing, null=True, blank=True)
    music = models.ForeignKey(Music, null=True, blank=True)
    studio = models.ForeignKey(Studio, null=True, blank=True)
    image = models.CharField(max_length=200, null=True, blank=True)

MovieForm

class MovieForm(ModelForm):

  class Meta:
    model = Movie
    exclude = ('slug', 'image')
    widgets = {
        'director': Select(attrs={'multiple class': 'chzn-select'}),
        'starring': Select(attrs={'multiple class': 'chzn-select'}),
        'producer': Select(attrs={'class': 'chzn-select'}),
        'writer': Select(attrs={'class': 'chzn-select'}),
        'studio': Select(attrs={'class': 'chzn-select'}),
        'editing': Select(attrs={'class': 'chzn-select'}),
        'screenplay': Select(attrs={'class': 'chzn-select'}),
        'music': Select(attrs={'class': 'chzn-select'}),
    }

Answer 1

The error message “Enter a list of values” implies the value returned from the form is not a instance of list or tuple, I think the problem is you use Select widget, which return a single value(” if empty), maybe you should use SelectMultiple:

class MovieForm(ModelForm):
    class Meta:
        model = Movie
        exclude = ('slug', 'image')
        widgets = {
            'director': SelectMultiple(attrs={'class': 'chzn-select'}),
            ...
        } 

Or you could manually convert the value to list/tuple before form clean.