Set default value or instance for django ModelForm ManyToMany field

Question

I have two models inn my django application where I have ManyToMany field in one model to other. I want to set the default for ManyToMany field but getting no way to do this.
My models are

Class Model1(models.Model):
    name = models.CharField(max_length=100)

class Model2(models.Model):
    model1 = models.ManyToManyField(Model1, null=True, blank=True, default=Model1.objects.first())

but using this I am getting this error

    raise AppRegistryNotReady("Models aren't loaded yet.")
    django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet.

I tried it by defining an explicit variable also like

m1 = Model1.objects.first()
and assigning this m1 variable to the field as default but same error again.

Please suggest how can I assign default value to the M2Mfield in django. I want that the first object of the choices should be selected when the modelform renders on template.

Answer 1

Given the way Django parses model class, you cannot do it like that, because "Models aren't loaded yet" <=> default are set at "parse time"

But you could use a callable as default.

def get_first_model1():
    return Model1.objects.first()

class Model2(models.Model):
    model1 = models.ManyToManyField(Model1, null=True, blank=True, default=get_first_model1)

It's the callable that you should use not the result value, thus the lack of parenthesis.

With this modification, default callable will be called at execution time when creating a new Model2 if you do not provide model1 attribute value.