Lesson 29 - Refactoring

LEARN

Today

• Refactoring
• Test-driven changes
• Convert to ForeignKey

Django for Beginners - Chapter 15

• Comments on Articles
• Articles app
• URL, Templates, Views
• ForeignKey - Comment, Article

Refactoring

• All code naturally decays
• Refactoring is needed to improve the structure while preserving functionality
• Design after the code is written

Martin Fowler

• Refactoring - Martin Fowler
• Defines why, when, and how to refactor

Why

• Incrementally improve code structure
• Preserve the usefulness of the code
• Protect the investment
• Refactoring is the single most important skill

When

• In preparation of new features
• When it gets hard
• After the features work

How

• Automated test rule - Test it or take it out
• Find duplicate code and dead code
• Remove it
• Test-driven development
• Test, Fix, Enhance, Improve (refactor)

Tests

• Do not refactor without tests
• Let the tests guide you
• Spot check with manual testing

BUILD

Visual Studio Code Tools

• Analysis
  • Peek/Go To Definition, Declaration, References
  • Show Call Hierarchy
• Refactoring
  • Extract Method
  • Extract Variable
  • Move Method
  • Rename

To Do

• Test
  • Build tests Author, Book Foreign Keys
  • Prep Manual Test script
• Extend
  • Convert Authors, Book, Chapters to use ForeignKey
• Improvements
  • Simplify and refactor

Demo Code

• Demo Code
• Follow along with my source code
• Clone my repo and edit the code

Author Data Model

Create a representation for Authors

python class Author(models.Model): name = models.CharField(max_length=200) user = models.ForeignKey(User, on_delete=models.CASCADE)

Book Data Model

Create a representation for Chapters in the Book

python class Book(models.Model): author = models.ForeignKey(Author, on_delete=models.CASCADE) title = models.CharField(max_length=200)

Chapter Data Model

Create a representation for Chapters in the Book

python class Chapter(models.Model): book = models.ForeignKey(Book, on_delete=models.CASCADE) order = models.IntegerField() title = models.CharField(max_length=200)

Author's Books

List the Book by an Author

book/views.py

```python

urls.py

path('author/', AuthorDetailView.as_view(), name='author_detail'),

class AuthorDetailView(DetailView): template_name = 'author_detail.html' model = Author

def get_context_data(self, **kwargs):
    author = Author.objects.get(pk=self.kwargs['pk'])
    return dict(object=author, books=Book.objects.filter(author=author))

```

Project 10 - Superhero News

• Views
  • Query for Articles about each Hero in HeroDetailView
  • Add the article list to hero detail template
• Data
  • Add hero as ForeignKey in Article
  • Migrate
• Tests
  • Hero Data
  • Hero Views
  • Article Data
  • Article Views

Project 10 - Views

• Superhero Selector Page
• Profile Tab
• News Tab
• Article Views
• Hero Views

Project 10 - Data

• Investigator Data Type
• Investigator <-- Hero <-- Article
• Views support proper queries
• Hero News  style

Project 10 - Tests

• Data/Views
• Investigator, Hero, Article