Django Girls Advanced - Models: Level 2

http://www.meetup.com/Taipei-py/events/225986103/

Transcript

1. Django Models
2. Django Models WELCOME TO LEVEL 2!
4. Django Models level 2 • SQL • Migrations • Relations (Basic)
5. SQL Database title content location My First Trip ᡙࢠ޷ծɼ٣ॄኄ޷䏆? ୆๺Րं᜾ Django େ๯ᯃ ኺᯩଶ౸ಈଶ ୆๺ࢢେ҆ე෮ڵೆ࿏ Ұஈ293ᥒ … … …
6. Post.objects.all() SELECT * FROM trips_post Python SQL * Rough translation
7. Post.objects.filter( location='ডӡେ҆᜾' ) SELECT * FROM trips_post WHERE location="ডӡେ҆᜾" Python SQL * Rough translation
8. ORM query SQL query Query results Model object Django Django SQL database
9. class Post(Model): title = CharField(max_length=100) content = TextField(blank=True) location = CharField(max_length=100)
10. class Post(Model): title = CharField(max_length=100) abstract = CharField( max_length=100, blank=True) content = TextField(blank=True) location = CharField(max_length=100)
11. >>> posts = Post.objects.all() >>> print(posts[0].abstract) Traceback (most recent call last): … django.db.utils.OperationalError: no such column: trips_post.abstract >>>
12. Migrations • When model change requires database change • Synchronisation • Schema or data migration
13. $ python manage.py makemigrations trips Migrations for 'trips': 0002_post_abstract.py: - Add field abstract to post
14. trips ├── __init__.py ├── admin.py ├── migrations │ ├── 0001_initial.py │ ├── 0002_post_abstract.py │ └── __init__.py ├── models.py ├── tests.py └── views.py
15. $ python manage.py migrate trips Operations to perform: Apply all migrations: trips Running migrations: Rendering model states... DONE Applying trips.0002_post_abstract... OK
16. >>> posts = Post.objects.all() >>> print(posts[0].abstract) >>>
18. Relational Database title author content location … Post name email Author
19. class Author(models.Model): name = models.CharField(max_length=50) email = models.EmailField() def __str__(self): return self.name
20. $ python manage.py makemigrations trips Migrations for 'trips': 0003_author.py: - Create model Author $ python manage.py migrate trips Operations to perform: Apply all migrations: trips Running migrations: Rendering model states... DONE Applying trips.0003_author... OK
21. >>> from trips.models import Author >>> Author.objects.create( ... name='Django Girls Taipei', ... email='taipei@djangogirls.org') <Author: Django Girls Taipei> >>>
22. class Author(models.Model): … class Post(models.Model): title = models.CharField(max_length=100) author = models.ForeignKey(Author) …
23. $ python manage.py makemigrations trips You are trying to add a non-nullable fi Please select a fix: 1) Provide a one-off default now (will 2) Quit, and let me add a default in m Select an option: _
24. $ python manage.py makemigrations trips You are trying to add a non-nullable fi Please select a fix: 1) Provide a one-off default now (will 2) Quit, and let me add a default in m Select an option: 1 Please enter the default value now, as The datetime and django.utils.timezone >>> 1
25. $ python manage.py makemigrations trips You are trying to add a non-nullable fi Please select a fix: 1) Provide a one-off default now (will 2) Quit, and let me add a default in m Select an option: 1 Please enter the default value now, as The datetime and django.utils.timezone >>> 1 Migrations for 'trips': 0004_post_author.py: - Add field author to post
26. $ python manage.py migrate trips Operations to perform: Apply all migrations: trips Running migrations: Rendering model states... DONE Applying trips.0004_post_author... OK
27. >>> from trips.models import Post >>> posts = Post.objects.all() >>> posts[0].author <Author: Django Girls Taipei> >>> posts[0].author.name 'Django Girls Taipei'
28. Exercises • Add abstract field in Post • Add Author model • Add author foreign key in Post • Display author in template
29. Hint <div class="author"> By <a href="mailto:{{ post.author.email }}"> {{ post.author.name }} </a> </div> templates/post.html