2017-07-19 Django

Django Models

Django models

Model names should be singular

It is a class inheriting from django.db.models.model

models.py:

from django.db import models

class Course(models.Model):
    created_at = models.DateTimeField(auto_now_add=True)
    title = models.CharField(max_length=255)
    description = models.TextField()

Attributes

Adding attributes to our class adds columns to our table

Migrate

After adding the model columns you need to migrate

./manage.py makemigrations
./manage.py migrate

Exploring the model

Enter the shell

>>> from courses.models import Course
# Get all instances
>>> Course.objects.all()
# Get an empty querySet
>>> c = Course()
>>> c.title = 'Python basics'
>>> c.description = 'Learn the basics of Python'
>>> c.save()
>>> Course.objects.all()

or

>>> Course(title="hello", description="hello").save()

or

>>> Course.objects.create(title="Hello", description="Learn about classes")

Sting representation

You can specify how django prints out the reference to the model instance

Using dunder str: def __str__(self):

Eg.

def str(self): return self.title

Find all model records

Course.objects.all()

Adding a foreign key

field_name = models.ForeignKey(Modelname)

If the associated model comes after the model declaration it must be in quotes

Example:

writer = models.ForeignKey('Writer')
course = models.ForeignKey(Course)