The document discusses Django's contenttypes framework which allows working with models generically without having to know the specific model being used. It presents several patterns for implementing generic functionality, including self-aware models, improved generic views, universal URLs, and dynamic forms. The key benefits are the ability to perform CRUD operations and create relationships between any objects without having to pre-program for each specific model.

2. POWERFUL GENERIC PATTERNS Django's Content Types Framework

3. CONTENTTYPES An application that can track all of the models installed in your Django-powered project, providing a high-level, generic interface for working with your models

4. SAY WHAT ?

5. CONTENTTYPES ---------------------------------------- | name | app_label | model | | post | blogger | post | | blog | blogger | Blog | | like | likeable | Like | ----------------------------------------

6. PROBLEM blog = Blog.objects.get( pk = 1 ) posts = Post.objects.filter( blog = blog ) features = Post.objects.filter( feature = True ) 3+ URLs 3+ view function 3+ templates

7. PROBLEM blog = Blog.objects.get( pk = 1 ) posts = Post.objects.filter( blog = blog ) features = Post.objects.filter( feature = True ) {%for post in posts %} {{ post.title }} {{ post.like_set.count }} likes {%endfor%}

8. GENERIC VIEWS?

9. GENERIC VIEWS? Take certain common idioms and patterns found in view development and abstract them so that you can quickly write common views of data without having to write too much code

10. GENERIC VIEWS? from django.views.generic import list_detail defmy_view( request ): return list_detail.object_list( queryset=Post.objects.all() )

11. NOT SO GENERIC VIEWS from django.views.generic import list_detail defmy_view( request ): return list_detail.object_list( queryset=Post.objects.all() )

12. NOT SO GENERIC VIEWS

14. A Model + ID

15. A Model + Slug

17. MORE PROBLEMS classFeature(models.Model): title = models.CharField() post = models.ForeignKey( Post ) likers = models.ForeignKey( User ) likes = models.IntegerField()

18. CONTENTTYPES An application that can track all of the models installed in your Django-powered project, providing a high-level, generic interface for working with your models

19. CONTENTTYPES Use the ORM without knowing what kind of objects you might be working with.

20. CONTENTTYPES Use the ORM without knowing what kind of objects you might be working with. EVER.

21. CONTENTTYPES Your Model ContentType Model A Model C Model B

22. GENERIC FOREIGNKEY from django.contrib.contenttypes.models importContentTypefrom django.contrib.contenttypes importgeneric classFeature(models.Model): content_type = models.ForeignKey (ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey( 'content_type' ,'object_id' )

23. MAGIC BITS classFeature(models.Model): content_type = models.ForeignKey (ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey( 'content_type' ,'object_id' )

24. MAGIC BITS classFeature(models.Model): content_type = models.ForeignKey (ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey( 'content_type' ,'object_id' )

25. MAGIC BITS classFeature(models.Model): content_type = models.ForeignKey (ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey( 'content_type' ,'object_id' )

26. GENERIC FOREIGNKEY >>> obj = Feature.objects.get( pk = 1 ) >>> obj.content_object >>> <Post: Hello World> >>> obj = Feature.objects.get( pk = 2 ) >>> obj.content_object >>> <Blog: The Best Blog> >>> obj = Feature.objects.get( pk = 3 ) >>> obj.content_object >>> <Anything: Whatever You Want>

27. GENERIC FOREIGNKEY

28. GENERIC FOREIGNKEY classPost(models.Model): title = models.CharField() blog = models.ForeignKey( Blog ) body = models.TextField() slug = models.SlugField() classLike( models.Model ): content_type = models.ForeignKey( ContentType ) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey( ... ) likers = models.ManyToMany( User )

29. GOTCHA! Models are NOT aware of their Content Type

30. MORE PROBLEMS classLike( models.Model ): content_type = models.ForeignKey( ContentType ) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey( ... ) likers = models.ManyToMany( User )

31. MORE PROBLEMS classLike( models.Model ): content_type = models.ForeignKey( ContentType ) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey( ... ) likers = models.ManyToMany( User ) deflike_view( request, object_id ): post = Post.objects.get( pk = object_id ) like = Like( object_id = post, ??? )

32. GENERIC GEMS from django.contrib.contenttypes.models importContentType from django.contrib.auth.models importUser >>> type = ContentType.objects.get_for_model( User ) >>> type >>> <ContentType: user > >>> model = type.model_class() >>> model >>> <class: 'django.contrib.auth.models.User'>

33. GENERIC GEMS

34. PATTERN #1

35. PATTERN #1 Self-Aware Model

36. SELF AWARE MODEL classSelfAwareModel(models.Model): def get_ct( self ): ''' Returns the Content Type for this instance''' return ContentType.objects.get_for_model(self) def get_ct_id( self ): ''' Returns the id of the content type for this instance''' return self.get_ct().pk def get_app_label( self ): return self.get_ct().app_label def get_model_name( self ): return self.get_ct().model classMeta: abstract = True

37. SELF AWARE MODEL classSelfAwareModel(models.Model): def get_ct( self ): ''' Returns the Content Type for this instance''' return ContentType.objects.get_for_model(self) def get_ct_id( self ): ''' Returns the id of the content type for this instance''' return self.get_ct().pk def get_app_label( self ): return self.get_ct().app_label def get_model_name( self ): return self.get_ct().model classMeta: abstract = True CACHED BY DJANGO

38. SELF AWARE MODEL classSelfAwareModel(models.Model): def get_ct( self ): ''' Returns the Content Type for this instance''' return ContentType.objects.get_for_model(self) def get_ct_id( self ): ''' Returns the id of the content type for this instance''' return self.get_ct().pk def get_app_label( self ): return self.get_ct().app_label def get_model_name( self ): return self.get_ct().model classMeta: abstract = True CACHED BY DJANGO self.__class__._cache[self.db][key]

39. SELF AWARE EVERYTHING classPost( SelfAwareModel ): title = models.CharField() blog = models.ForeignKey( Blog ) body = models.TextField() slug = models.SlugField() likers = models.ForeignKey( User ) likes = models.IntegerField()

40. SELF AWARE EVERYTHING classPost( SelfAwareModel ): title = models.CharField() blog = models.ForeignKey( Blog ) body = models.TextField() slug = models.SlugField() likers = models.ForeignKey( User ) likes = models.IntegerField() ALL MODELS SUBCLASSE SELFAWAREMODEL

41. SELF AWARE EVERYTHING classPost( SelfAwareModel ): title = models.CharField() blog = models.ForeignKey( Blog ) body = models.TextField() slug = models.SlugField() likers = models.ForeignKey( User ) likes = models.IntegerField() @permalink def get_absolute_url( self ): ... >>> post = Post.objects.latest() >>> obj.get_ct() >>> <ContentType: post>

42. SELF AWARE EVERYTHING classPost( SelfAwareModel ): title = models.CharField() blog = models.ForeignKey( Blog ) body = models.TextField() slug = models.SlugField() likers = models.ForeignKey( User ) likes = models.IntegerField() @permalink def get_absolute_url( self ): ... I KNOW MY CONTENT TYPE >>> post = Post.objects.latest() >>> obj.get_ct() >>> <ContentType: post>

43. HOORAY!

44. PATTERN #2 REAL Generic Views

45. REAL GENERIC VIEW defobject_list( request, ct_id ... ): type = ContentType.objects.get( pk = ct_id ) model = type.model_class() obj_list = model._default_manager.all() return render_to_response( ... )

46. REAL GENERIC VIEW defobject_detail( request, ct_id, obj_id, template=None ): type = ContentType.objects.get( pk = ct_id ) model = type.model_class() obj = model._default_manager.get( pk = ct_id ) if template isNone: template = '%s_detail.html'%(type) return render_to_response( template )

47. REAL GENERIC VIEW defobject_detail( request, ct_id, obj_id, template=None ): type = ContentType.objects.get( pk = ct_id ) model = type.model_class() obj = model._default_manager.get( pk = ct_id ) if template isNone: template = '%s_detail.html'%(type) return render_to_response( template )

48. REAL GENERIC VIEW defobject_detail( request, ct_id, obj_id, template=None ): type = ContentType.objects.get( pk = ct_id ) model = type.model_class() obj = model._default_manager.get( pk = ct_id ) if template isNone: template = '%s_detail.html'%(type) return render_to_response( template ) Might Want To Cache That

51. MORE PROBLEMS Blog Post Post Likes Post Likers

52. MORE PROBLEMS Blog Post Post Likers Post Likes

53. LESS PROBLEMS LIKE ContentType POST ANYTHING FEATURE

54. LIKE ANYTHING YOU WANT

55. NOT BAD, KID!

56. PATTERN #3 Universal URLs

57. UNIVERSAL URLs urlpatterns = patterns( 'myproj.myapp', url( r'^(?P<slug>[-]+)/(?P<ct_id>+)/list/$', 'object_list', name='my_proj_content_list' ), url( r'^(?P<slug>[-]+)/(?P<ct_id>+)-(?P<obj_id>+)/$', 'object_detail', name="my_proj_content_detail" ), url( r'^(?P<slug>[-]+)/(?P<ct_id>+)-(?P<obj_id>+)/edit/$', 'object_edit', name="my_proj_content_edit" ) ... )

58. UNIVERSAL URLs /something-here/23/list/ /some-title/23-21/ /some-title/23-21/edit/ /some-title/23-21/delete/ /some-title/23-21/blah/

59. PATTERN #4 Magic Forms

60. MAGIC FORMS defedit_object( request, ct_id, obj_id ): obj = utils.get_object( ct_id, obj_id )

61. MAGIC FORMS defedit_object( request, ct_id, obj_id ): obj = utils.get_object( ct_id, obj_id ) form = ???

62. MAGIC FORMS defedit_object( request, ct_id, obj_id ): obj = utils.get_object( ct_id, obj_id ) form = ??? Can't predefine ModelForm when you don't know what model you're working with

63. MAGIC FORMS

64. MAGIC FORMS defform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class() class_MagicForm(forms.ModelForm): ... classMeta: model= modelclass if includes: fields = includes if excludes: exclude = excludes return _MagicForm

65. MAGIC FORMS defform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class() class_MagicForm(forms.ModelForm): ... classMeta: model= modelclass if includes: fields = includes if excludes: exclude = excludes return _MagicForm DON'T KNOW

66. MAGIC FORMS defform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class() class_MagicForm(forms.ModelForm): ... classMeta: model= modelclass if includes: fields = includes if excludes: exclude = excludes return _MagicForm DON'T CARE

67. MAGIC FORMS defform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class() class_MagicForm(forms.ModelForm): ... classMeta: model= modelclass if includes: fields = includes if excludes: exclude = excludes return _MagicForm PERFECTLY LEGAL

68. FULL CIRCLE defedit_object( request, ct_id, obj_id ): obj = utils.get_object( ct_id, obj_id ) formclass = utils.get_form_for( obj ) form = formclass() return render_to_response( ... {'form':form} )

69. FULL CIRCLE defedit_object( request, ct_id, obj_id ): obj = utils.get_object( ct_id, obj_id ) formclass = utils.get_form_for( obj ) form = formclass() return render_to_response( ... {'form':form} ) DON'T KNOW

70. FULL CIRCLE defedit_object( request, ct_id, obj_id ): obj = utils.get_object( ct_id, obj_id ) formclass = utils.get_form_for( obj ) form = formclass() return render_to_response( ... {'form':form} ) DON'T CARE

71. DEAD SIMPLE {%urlmy_proj_content_list ct_id=obj.get_ct_id %} {%urlmy_proj_content_detail slug=obj.slug, ct_id=obj.get_ct_id, obj_id=obj.pk %} {%urlmy_proj_content_edit slug=obj.slug, ct_id=obj.get_ct_id, obj_id=obj.pk %}

72. FOR THE WIN

73. SCALE IT OUT Define A Model Sync DB Make A Template ( Maybe ? ) Rinse Repeate

75. Better Generic Views & utilities

76. Universial URLs

78. Better Generic Views & utilities

79. Universial URLs

80. Magic FormsYou can perform CRUD ops and create any kind of relationship on any kind of object at anytimewithout programming for every situation.

81. FIN