Why does adding this __init__() method break my Django model?

Question

This question is a follow-up to one I asked earlier here.

I have a Django model as follows:

class MyModel(models.Model):
    my_field1 = models.DateTimeF         


        

Answer 1

Although, you're strongly advised to use a classmethod or a custom manager in the docs, your code would not work because you have modified the calling signature of the superclass, which should have been:

super(MyModel, self).__init__(*args, **kwargs)

You can avoid doing this by using a classmethod:

class MyModel(models.Model):
    my_field1 = models.DateTimeField(default=datetime.utcnow, editable=False)
    my_field2 = models.DateTimeField()

    @classmethod
    def sync_dates(cls, myfield1):
         my_model = cls(my_field1=myfield1, my_field2=myfield1)
         # do something with my_model
         return my_model

And MyModel.sync_dates(some_date) does the trick.

Or you could use a custom manager which is the preferred way:

class MyModelManager(models.Manager):
    def create_with_sync_date(self, myfield1):
        my_model = self.create(my_field1=myfield1, my_field2=myfield1)
        # do something with my_model
        return my_model

class MyModel(models.Model):
    my_field1 = models.DateTimeField(default=datetime.utcnow, editable=False)
    my_field2 = models.DateTimeField()

    objects_synced = MyModelManager()

And you can call MyModel.objects_synced.create_with_sync_date(some_date)

Answer 2

You don't need to use __init__ in Django models, instead use Meta class

class MyModel(models.Model):
    my_field1 = models.DateTimeField(default=datetime.utcnow, editable=False)
    my_field2 = models.DateTimeField()

    class Meta:
        verbose_name = 'My Model'
        verbose_name_plural = 'My Models' # and so on

Answer 3

Using init is discouraged. According to Django docs:

https://docs.djangoproject.com/en/1.9/ref/models/instances/#creating-objects

from django.db import models

class Book(models.Model):
    title = models.CharField(max_length=100)

    @classmethod
    def create(cls, title):
        book = cls(title=title)
        # do something with the book
        return book

 book = Book.create("Pride and Prejudice")