Lesson 14 - Manipulating Data

LEARN

Week 5 - Data

• Lesson 12 - Data CRUD Operations
• Lesson 13 - View Inheritance
• Lesson 14 - Manipulating Data
• Project 5 - Admin Views and View Inheritance
• Django for Beginners - Chapter 5 - Blog App

Project 4

• Project 4 requirements do not require a database
• Key Requirements
  • List of hero with links
  • Details pages for all heros
  • Include a photo that is stored on your server

Project 5

• Key Requirements
  • Admin views to create database for heroes
  • List of hero with links from database
  • Details pages for all heros from database
  • Include a photo that is stored on your server
  • View Inheritance (hero_theme.html)

Data Models

• ORM lets us write Data Models as Python Classes
• Database is automatically updated
• Migration updates the tables

Data Migrations

Create the scripts to update the database

Apply the migrations

python manage.py makemigrations hero

python manage.py migrate

CRUD

• CREATE - make a new record
• READ - get one or more records
• UPDATE - modify an existing record
• DELETE - remove a record

Django Shell

A console window will let you execute Python code directly

Do all the CRUD operations

python manage.py shell

Data Model

• Superhero (name, identity)

hero/models.py

class Superhero(models.Model):
    name = models.CharField(max_length=20)
    identity = models.CharField(max_length=20)

CREATE

hero/hero.py

from .models import Superhero

def add_hero(hero_name, hero_id):
    return Superhero.objects.create(name=hero_name, identity=hero_id)

READ - List

hero/hero.py

def list_heroes():
    return Superhero.objects.all()

READ - Get

hero/hero.py

def get_hero(pk):
    return Superhero.objects.get(pk=pk)

def get_identity(id):
    return Superhero.objects.get(identity=id)

def get_hero_name(supername):
    return Superhero.objects.get(name=supername)

UPDATE

hero/hero.py

def set_hero_id(pk, id):
    w = get_hero(pk)
    w.identity=id
    w.save()

def set_hero_name(pk, name):
    w = get_hero(pk)
    w.name=name
    w.save()

DELETE

hero/hero.py

def delete_hero(pk):
    Superhero.objects.get(pk=pk).delete()

BUILD

Test CRUD

Use Django Tests to test the CRUD operations

hero/tests.py

from django.test import TestCase

from .models import Superhero
from .hero import list_heroes

class CrudTests(TestCase):

    def test_num_heroes(self):
        num_heroes = len(list_heroes())
        self.assertEqual(num_heroes, 0)

Test Each Operation

Test every function you write

def test_hero_model(self):
    pass

def test_create(self):
    pass

def test_read(self):
    pass

def test_update(self):
    pass

def test_delete(self):
    pass

Use the Query Functions

• Tests the functions
• Provides place to put business logic
• Enable tests in small steps

You practice

• Create access functions in hero/hero.py
• Build tests in hero/tests.py
• Debug tests and functions one at a time
• Create five tests (model, create, read, update, delete)