Powerful Generic Patterns With Django
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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.
![SELF AWARE MODELclassSelfAwareModel(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().pkdef get_app_label( self ):return self.get_ct().app_labeldef get_model_name( self ):return self.get_ct().modelclassMeta: abstract = TrueCACHED BY DJANGOself.__class__._cache[self.db][key]](https://image.slidesharecdn.com/mkemeetup-contenttypes-7-13-2011-110713225855-phpapp02/85/Powerful-Generic-Patterns-With-Django-38-320.jpg)
![REAL GENERIC VIEWdefobject_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 Thatself.__class__._cache[self.db][key]](https://image.slidesharecdn.com/mkemeetup-contenttypes-7-13-2011-110713225855-phpapp02/85/Powerful-Generic-Patterns-With-Django-49-320.jpg)
![UNIVERSAL URLsurlpatterns = patterns( 'myproj.myapp', url( r'^(?P<slug>[-\w]+)/(?P<ct_id>\d+)/list/$', 'object_list',name='my_proj_content_list' ), url( r'^(?P<slug>[-\w]+)/(?P<ct_id>\d+)-(?P<obj_id>\d+)/$','object_detail',name="my_proj_content_detail" ), url( r'^(?P<slug>[-\w]+)/(?P<ct_id>\d+)-(?P<obj_id>\d+)/edit/$', 'object_edit',name="my_proj_content_edit" ) ...)](https://image.slidesharecdn.com/mkemeetup-contenttypes-7-13-2011-110713225855-phpapp02/85/Powerful-Generic-Patterns-With-Django-57-320.jpg)
![MAGIC FORMSdefform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class()class_MagicForm(forms.ModelForm): ...classMeta: model= modelclassif includes: fields = includesif excludes: exclude = excludes return _MagicForm](https://image.slidesharecdn.com/mkemeetup-contenttypes-7-13-2011-110713225855-phpapp02/85/Powerful-Generic-Patterns-With-Django-64-320.jpg)
![MAGIC FORMSdefform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class()class_MagicForm(forms.ModelForm): ...classMeta: model= modelclassif includes: fields = includesif excludes: exclude = excludes return _MagicFormDON'T KNOW](https://image.slidesharecdn.com/mkemeetup-contenttypes-7-13-2011-110713225855-phpapp02/85/Powerful-Generic-Patterns-With-Django-65-320.jpg)
![MAGIC FORMSdefform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class()class_MagicForm(forms.ModelForm): ...classMeta: model= modelclassif includes: fields = includesif excludes: exclude = excludes return _MagicFormDON'TCARE](https://image.slidesharecdn.com/mkemeetup-contenttypes-7-13-2011-110713225855-phpapp02/85/Powerful-Generic-Patterns-With-Django-66-320.jpg)
![MAGIC FORMSdefform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class()class_MagicForm(forms.ModelForm): ...classMeta: model= modelclassif includes: fields = includesif excludes: exclude = excludes return _MagicFormPERFECTLYLEGAL](https://image.slidesharecdn.com/mkemeetup-contenttypes-7-13-2011-110713225855-phpapp02/85/Powerful-Generic-Patterns-With-Django-67-320.jpg)
Powerful Generic Patterns With Django
- 2. POWERFUL GENERIC PATTERNSDjango's Content Types Framework
- 3. CONTENTTYPESAn 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. PROBLEMblog = Blog.objects.get( pk = 1 )posts = Post.objects.filter( blog = blog )features = Post.objects.filter( feature = True )3+ URLs3+ view function3+ templates
- 7. PROBLEMblog = 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%}
- 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_detaildefmy_view( request ):return list_detail.object_list( queryset=Post.objects.all() )
- 11. NOT SO GENERIC VIEWSfrom django.views.generic import list_detaildefmy_view( request ):return list_detail.object_list( queryset=Post.objects.all() )
- 12. NOT SO GENERIC VIEWS
- 13. NOT SO GENERIC VIEWSTo Use A Generic View You Need...A Queryset
- 14. A Model + ID
- 15. A Model + Slug
- 16. A Model + Slug FieldMORE PROBLEMSclassPost(models.Model): title = models.CharField() blog = models.ForeignKey( Blog ) body = models.TextField() slug = models.SlugField() likers = models.ForeignKey( User ) likes = models.IntegerField()BlogPostPost LikesPost Likers
- 17. MORE PROBLEMSclassFeature(models.Model): title = models.CharField() post = models.ForeignKey( Post ) likers = models.ForeignKey( User ) likes = models.IntegerField()
- 18. CONTENTTYPESAn 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. CONTENTTYPESUse the ORM without knowing what kind of objects you might be working with.
- 20. CONTENTTYPESUse the ORM without knowing what kind of objects you might be working with. EVER.
- 21. CONTENTTYPESYour ModelContentTypeModel AModel CModel B
- 22. GENERIC FOREIGNKEYfrom django.contrib.contenttypes.models importContentTypefrom django.contrib.contenttypes importgenericclassFeature(models.Model): content_type = models.ForeignKey (ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type' ,'object_id' )
- 23. MAGIC BITSclassFeature(models.Model): content_type = models.ForeignKey (ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey( 'content_type' ,'object_id' )
- 24. MAGIC BITSclassFeature(models.Model): content_type = models.ForeignKey (ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type' ,'object_id' )
- 25. MAGIC BITSclassFeature(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>
- 28. GENERIC FOREIGNKEYclassPost(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 PROBLEMSclassLike( models.Model ): content_type = models.ForeignKey( ContentType ) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey( ... ) likers = models.ManyToMany( User )
- 31. MORE PROBLEMSclassLike( 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 GEMSfrom django.contrib.contenttypes.models importContentTypefrom 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
- 36. SELF AWARE MODELclassSelfAwareModel(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().pkdef get_app_label( self ):return self.get_ct().app_labeldef get_model_name( self ):return self.get_ct().modelclassMeta: abstract = True
- 37. SELF AWARE MODELclassSelfAwareModel(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().pkdef get_app_label( self ):return self.get_ct().app_labeldef get_model_name( self ):return self.get_ct().modelclassMeta: abstract = TrueCACHED BY DJANGO
- 38. SELF AWARE MODELclassSelfAwareModel(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().pkdef get_app_label( self ):return self.get_ct().app_labeldef get_model_name( self ):return self.get_ct().modelclassMeta: abstract = TrueCACHED BY DJANGOself.__class__._cache[self.db][key]
- 39. SELF AWARE EVERYTHINGclassPost( SelfAwareModel ): title = models.CharField() blog = models.ForeignKey( Blog ) body = models.TextField() slug = models.SlugField() likers = models.ForeignKey( User ) likes = models.IntegerField()
- 40. SELF AWARE EVERYTHINGclassPost( SelfAwareModel ): title = models.CharField() blog = models.ForeignKey( Blog ) body = models.TextField() slug = models.SlugField() likers = models.ForeignKey( User ) likes = models.IntegerField()ALL MODELSSUBCLASSESELFAWAREMODEL
- 41. SELF AWARE EVERYTHINGclassPost( SelfAwareModel ): title = models.CharField() blog = models.ForeignKey( Blog ) body = models.TextField() slug = models.SlugField() likers = models.ForeignKey( User ) likes = models.IntegerField()@permalinkdef get_absolute_url( self ): ...>>> post = Post.objects.latest()>>> obj.get_ct()>>> <ContentType: post>
- 42. SELF AWARE EVERYTHINGclassPost( SelfAwareModel ): title = models.CharField() blog = models.ForeignKey( Blog ) body = models.TextField() slug = models.SlugField() likers = models.ForeignKey( User ) likes = models.IntegerField()@permalinkdef get_absolute_url( self ): ...I KNOW MYCONTENT TYPE>>> post = Post.objects.latest()>>> obj.get_ct()>>> <ContentType: post>
- 43. HOORAY!
- 44. PATTERN #2REAL Generic Views
- 45. REAL GENERIC VIEWdefobject_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 VIEWdefobject_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 VIEWdefobject_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 VIEWdefobject_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
- 49. REAL GENERIC VIEWdefobject_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 Thatself.__class__._cache[self.db][key]
- 50. cPickle & noSQL DB ( Redis )REAL GENERIC VIEWproject|| - likeables/|| - blog/ | |- templates/ | |- blog/ | -post_list.html | -post_detail.html | -urls.py|| - templates/| - object_list.html| - object_detail.html| - urls.py
- 51. MORE PROBLEMSBlogPostPost LikesPost Likers
- 52. MORE PROBLEMSBlogPostPost LikersPost Likes
- 54. LIKE ANYTHING YOU WANT
- 55. NOT BAD, KID!
- 57. UNIVERSAL URLsurlpatterns = patterns( 'myproj.myapp', url( r'^(?P<slug>[-\w]+)/(?P<ct_id>\d+)/list/$', 'object_list',name='my_proj_content_list' ), url( r'^(?P<slug>[-\w]+)/(?P<ct_id>\d+)-(?P<obj_id>\d+)/$','object_detail',name="my_proj_content_detail" ), url( r'^(?P<slug>[-\w]+)/(?P<ct_id>\d+)-(?P<obj_id>\d+)/edit/$', 'object_edit',name="my_proj_content_edit" ) ...)
- 60. MAGIC FORMSdefedit_object( request, ct_id, obj_id ): obj = utils.get_object( ct_id, obj_id )
- 61. MAGIC FORMSdefedit_object( request, ct_id, obj_id ): obj = utils.get_object( ct_id, obj_id ) form = ???
- 62. MAGIC FORMSdefedit_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 FORMSdefform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class()class_MagicForm(forms.ModelForm): ...classMeta: model= modelclassif includes: fields = includesif excludes: exclude = excludes return _MagicForm
- 65. MAGIC FORMSdefform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class()class_MagicForm(forms.ModelForm): ...classMeta: model= modelclassif includes: fields = includesif excludes: exclude = excludes return _MagicFormDON'T KNOW
- 66. MAGIC FORMSdefform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class()class_MagicForm(forms.ModelForm): ...classMeta: model= modelclassif includes: fields = includesif excludes: exclude = excludes return _MagicFormDON'TCARE
- 67. MAGIC FORMSdefform_class_for( obj, includes=[] excludes=[] ): modelclass = obj.get_ct().model_class()class_MagicForm(forms.ModelForm): ...classMeta: model= modelclassif includes: fields = includesif excludes: exclude = excludes return _MagicFormPERFECTLYLEGAL
- 68. FULL CIRCLEdefedit_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 CIRCLEdefedit_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 CIRCLEdefedit_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'TCARE
- 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 OUTDefine A ModelSync DBMake A Template ( Maybe ? )Rinse Repeate
- 74. PATTERNS RECAPSelf Aware Models
- 75. Better Generic Views & utilities
- 76. Universial URLs
- 77. Magic FormsPATTERNS RECAPSelf Aware Models
- 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