Generic method that can take any Django Model and provide information about manytomany field.

[Akshay Gaur]

Also posted here : https://stackoverflow.com/questions/52280584/any-way-to-fetch-the-through-fields-for-an-object-linked-via-many2many-field-wit

I am trying to write a generic method that can take any Django Model and returns it in a dictionary form.

So for example, if my models are defined thus (very generic):

    class A(models.Model):

        somefieldA = models.TextField()

        m2mfield = models.ManyToManyField(B, through='AandB')

        def __unicode__(self):

            return self.somefieldA

    

    class B(models.Model):

        somefieldB = models.TextField()

        def __unicode__(self):

            return self.somefieldB

    class AandB(models.Model):

        a = models.ForeignKey(A)

        b = models.ForeignKey(B)

        field1 = models.DecimalField()

        field2 = models.TextField()

        field3 = models.DateField()

Now, assume we have an instance of the object A `a_obj`.

I can get all the related B objects using:

    # This loop is there because I am working with other fields as well.

    def instance_to_dict(instance)

    for field in instance._meta.get_fields():

        if field.many_to_many:

             m2m_mgr = getattr(instance, field.name)

             for idx, assoc_obj in enumerate(m2m_mgr.all()):

                 assoc_obj_str = str(assoc_obj)

                 # How to obtain the related through field values?

                 # m2m_mgr.through.objects.get() would need prior knowlegde

                 # of field name which is something I don't have in advance.

                 # m2m_mgr.through.objects.all() fetches all the objects

                 # in the table.

And then call `instance_to_dict(a_obj)`. This method could be called by passing other models' instances.

Ideally, I would like to be able to access related "through" fields for any object. Is this possible to do?