Object Oriented Views / Aki Salmi
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Introducing Exhibit pattern. Or how to program controllers and views in such a way that you don't need that many if-statements. Fully Test-Driven solution.
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Object Oriented Views / Aki Salmi
- 2. I like to do crazy stuff codefreeze.fi experimental coding
- 3. Programmer @Ambientia skype: rinkkasatiainen twitter: @rinkkasatiainen web: rinkkasatiainen.fi email: aki.salmi@iki.fi
- 5. Goal for this talk
- 6. is to
- 10. Content • Background • A way to solve • Discussion • Open Space: Mob Programming?
- 11. Very Brief Background • Confluence plugin • real production code (used by thousands, daily)
- 12. We have all seen
- 13. Controllers like
- 14. This
- 15. /INDEX (1 of many actions) Params Service “DAO” “or not DAO” DAO-DAO-DAO Service Service Domain Service Render
- 16. Not that, not today
- 17. Let’s assume we’re working with thin controllers
- 18. Have we seen
- 19. views like
- 20. this Only today: logic in a view
- 21. So how then?
- 22. How about Code I’ve written myself?
- 23. Not much better
- 24. A Deeper Dive Params BUILD CONTEXT GET MODEL RENDER OR RENDER
- 25. But there is a catch
- 26. Render Many Blogs Or 1, or 0
- 27. ... based on object types
- 28. Build a ‘different’ domain entity? Build ‘real’ Domain Build ‘real’ Domain
- 31. Seems like a violation of SRP (Single Responsibility Principle)
- 32. What did we see • build parameters • build context (on 2 places) • build domain • render different data, differently, based on the domain entity
- 33. Visually Controller HTTP GET Domain View 0 View 1 View N
- 34. It works
- 35. ..sort of • most of the bugs I introduced, were on this behavior of the system. • This class • Concepts introduced by this class • Integration with Confluence API • especially ‘null’s
- 36. What IF Controller HTTP GET Domain View 0 View 1 View N
- 37. What IF... C’s responsibility • Given a set of parameters... • Build Model (service / repository) • Render Template with model given • and let other’s to figure out which is the view to render
- 38. Decorate / Exhibit Controller HTTP GET Domain View Exhibit 1) build model 2) render 3) exhibit View tmpl 4) render
- 39. How does it work
- 40. few design decision done by me • avoid nulls • separate Read Model from Write Model • 1st class collections • Separated Query and Command Controller (sort of CQRS)
- 41. Domain Entity: Group <if> ReadOrWriteModel <if> ReadModel <if> WriteModel GroupEntity GroupDescrGroupList
- 42. Domain Entity: Group <if> ReadOrWriteModel <if> ReadModel <if> WriteModel GroupEntity GroupDescrGroupList
- 43. Domain Entity: Group GroupEntity * immutable * final private prop * behavior rich GroupDescriptor * public properties * tiny behavior AGroupThatDoes NotExistYet AGroup
- 44. Domain Entity: Group <if> ReadOrWriteModel <if> ReadModel <if> WriteModel GroupEntity GroupDescrGroupList
- 45. Domain Entity: Group GroupList * behavior: iterate
- 46. Introducing Exhibits • Introduced by Avdi Grimm • sort of presenter-decorator
- 47. Exhibit Characteristics • Wraps a single model instance • Is a true Decorator • Brings together model and context • Encapsulates the decision about how to render an object • May modify the behavior of an object
- 48. Exhibit B Exhibit A Exhibit visually Model object
- 49. Exhibits: Group <if> Exhibit + renderBody() GroupListExh GroupList GroupExhibit GroupEntity EditGroupExh GroupDesc GroupWPicture
- 50. Exhibits: Group GroupListExh ListView GroupExhibit GroupView EditGroupExh EditGroup GroupWPicture GPictureView
- 51. REST view HTTP PATH Contr#Action Domain Class GET /foo(.:format) foos#index FooList POST /foo(.:format) foos#create FooDescriptor GET /foo/new foos#new FooDescriptor GET /foo/:id/edit foos#edit FooDescriptor GET /foo/:id foos#show FooEntry PATCH/PUT /foo/:id foos#update FooDescriptor DELETE /foo/:id foos#delete FooDescriptor
- 52. Creating exhibits the ruby way 1/2 Avdi Grimm: Object on Rails, Listing 76
- 53. Creating exhibits the ruby way 2/2 Avdi Grimm: Object on Rails, Listing 77
- 54. Creating exhibits the Java 8 way 1/N
- 55. Time for some code Confluence plugin Velocity templates
- 56. View
- 57. Controller
- 58. Exhibit A
- 59. Exhibit B
- 60. Exhibit C
- 61. Exhibit D
- 62. Decorate / Exhibit Controller HTTP GET Domain View Exhibit 1) build model 2) render 3) exhibit View tmpl 4) render
- 63. And visually
- 66. Did it work - in retrospect • No issues in production with this code • It is not, by far, easy to grasp. Without someone explaining
- 67. What I did not show • transformations of domain entities: • Request -> Write -> Persistence • Persistence -> Write (-> Read) • Composite Exhibit - how to show 0, 1 or many concepts, dynamically, based on the ModelObject rendered
- 68. What could I experiment • Capabilities for exhibits • Capability.mobile • Capability.REST • Capability.json
- 69. Thanks! Questions? skype: @rinkkasatiainen twitter: @rinkkasatiainen email: aki.salmi@iki.fi