Lesson 32 - Code Generator

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Course Content

• Course Content

Today

• Code Cloner Design Pattern

Design Patterns

• Capture design decisions for next time
• Reuse design choices
• Custom choices and limitations
• When to apply pattern
• Say it in code

Reusable Design Patterns

• CRUD Operations
• CRUD Test
• Data Views
• Data Views Test
• Import/Export
• Code Cloner

Book Data Relationships

If you have more that four data models draw a simple diagram

Use https://www.gliffy.com/

Superhero Data Relationships

Use https://www.gliffy.com/

Problem

• Add a new data type
• Don't repeat work
• Reduce from 1 day to 1 hour

Code Cloner Design Pattern

• Why use this pattern
• When to use code cloning
• How to steps
• What to focus on

Code Cloner - Why

• Encapsulate your design patterns
• Say it in code
• Write software to write software
• Own it and change it

Code Cloner - When

• You have files capture a design idea
• You want to make mechanical/simple changes
• Instantly generate a 90% solution

Code Cloner - How

• Select the code to leverage
• Choose the files
• Convert the files
• Integrate in structure
• Test and fix

Code Cloner - What

• Understand the choices
• Start with working code
• Understand the limitation
• Make improvements to the code generator

Version Control

• Commit before cloning
• Commit after cloning
• Commit after debugging new tests
• Don't lose any work

Create a Django Command

• Build a custom command to run the cloner

coder/management/commands/cloner.py

```python from django.core.management.base import BaseCommand

class Command(BaseCommand):

def handle(self, *args, **options):
    print("CODE CLONER")
    generate_code()

```

Invoke the cloner

bash $ python manage.py cloner

Create the Data Model

book/models.py

python class Note(models.Model): chapter = models.ForeignKey(Chapter, on_delete=models.CASCADE, editable=False) author = models.ForeignKey(Author, on_delete=models.CASCADE, editable=False) title = models.CharField(max_length=200) text = models.TextField()

Select the code to leverage

• Find the closest match to your new needs
• Locate URLs, views, templates
• Clone Book --> Note

book/urls_book.py book/views_book.py book/tests_book.py templates/book_add.html templates/book_delete.html templates/book_detail.html templates/book_edit.html templates/book_list.html

Choose the files

• Map the old files to new files

book/urls_book.py --> book/urls_note.py book/views_book.py --> book/views_note.py book/tests_book.py --> book/tests_note.py templates/book_add.html --> templates/note_add.html templates/book_delete.html --> templates/note_delete.html templates/book_detail.html --> templates/note_detail.html templates/book_edit.html --> templates/note_edit.html templates/book_list.html --> templates/note_list.html

Convert the files

• Convert each code file using replace

python def convert_file(f1, f2, object1, object2, class1, class2): text = open(f1).read() text = text.replace(object1, object2) text = text.replace(class1, class2) open(f2, 'w').write(text) print(f'{f1} --> {f2}')

Convert all files

• Convert all selected files

python def clone_code(class_name, object_name, old_class, old_object): print(f'\n\nGenerating code \nClass: {class_name}, Object: {object_name}\n') copyfile(f'{old_object}/urls.py', f'{old_object}/urls_{old_object}.py') for f in file_list(old_object).split('\n'): new_file = f.replace(old_object, object_name).replace(f'{object_name}/', f'{old_object}/') convert_file(f, new_file, old_object, object_name, old_class, class_name)

Perform Clone Operation

• Set up the config so that it can be rerun

python def generate_code(): class_name = "Note" object_name = "note" old_class = 'Book' old_object = 'book' clone_code(class_name, object_name, old_class, old_object)

Integrate in structure

• Debug stand-alone views
• Strip out unneeded logic
• Build desired workflow
• Simplify the code
• Improve the generator logic

Test and fix

• Start with generated tests
• Comment out all code
• Add one function in at a time
• Add specific test logic

BUILD

Demo Code

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

Final Project

• Due on December 3
• Requirements for Projects 10, 11, 12, 13, 14
• Partial Credit will be given