Leveraging Rails

Patterns to Enhance your MVC

Transcript

1. Scott Johnson Leveraging Rails Patterns to ! enhance your MVC
2. Greatness of Rails
3. Three Patterns ❖ Null Objects! ❖ Remote Facades! ❖ Data Context Interactions (DCI) / SOLID
4. ImageSet Null Object a Null Object is an object with defined neutral (‘null’) behavior.! ! ! ! — Wikipedia
5. Symptoms ❖ Lots of nil? or present?
8. Address Remote Facade Provides a coarse-grained facade on fine-grained objects to improve efficiency over a network! ! ! — Martin Fowler
9. Address street = ! city = ! zip = ! street! city! zip AddressFacade address! update_attributes
10. Description The most common use of this pattern is is between a presentation and a domain model…! Design an application without distribution, then layer the distribution ability on top of it with Remote Facades and Data Transfer Objects! — Martin Fowler
11. Address Facade A facade is an object that provides a simplified interface to a larger body of code! ! ! — Wikipedia
13. Data Model Facade Role Model Model View Web Controller Role Role ❖ display_value! ❖ display_name
14. Symptoms ❖ Identity Crisis! ❖ Fat Controllers! ❖ Logic in views! ❖ Display logic in models
16. DCI & SOLID Your design task is to recognize that a role exists, define the interface of its duck type and provide an implementation of that interface for every possible player! — Sandi Metz
17. Symptoms
18. Description ❖ DCI (Trygve Reenskaug, Jim Coplien)! ❖ Clean Ruby (Jim Gay)! ❖ SOLID! ❖ Uncle Bob! ❖ Sandi Metz
19. IS ! vs ! DOES
20. Brain Rules Video http://www.youtube.com/watch?v=mzbRpMlEHzM
21. Purpose The purpose of DCI is to produce code that a person can read and understand and so reason about its correctness! — Trygve Reenskaug
22. Account ❖ Balance! ❖ Currency! ❖ Add! ❖ Deduct! ! ❖ Transfer(destination_account)
23. AccountTransfer ❖ Call(source_account, destination_account)
24. Clean Ruby While simple models may support combining data and behavior in one class, doing so can lead to difficulty in responding to change later. The classes that we begin to define should represent data or model the behavior of the data object, but not both. — Jim Gay p. 24
25. Clean Ruby This is where the ideas in DCI can help improve our architecture. In our example we have two accounts where one acts as the source and the other acts as the destination for the transfer of funds… The context is the object responsible for organizing the data and roles for carrying out your use cases. It’s a powerful model for encapsulating your business logic because it gives you a clear way to organize the interactions of objects in your system. ! — Jim Gay p. 37
26. Data Model Context / Interaction Role Model Model Role Role Controller Web
27. Data Model Facade Role Model Model Role Role View Web Controller
28. Data Model Context / Interaction Role Model Model Role Role Controller Web
29. Example ❖ Context! ❖ Roles
30. Implementation ❖ Write context as module and extend it on instances when they take on a role! ❖ Class methods vs instance methods! ❖ Composition & Duck Typing
31. Composition & Duck Typing ❖ SOLID! ❖ Roles! ❖ http://mikepackdev.com/ blog_posts/24-the-right-way- to-code-dci-in-ruby
32. SOLID ❖ Single Responsibility! ❖ Open/Closed! ❖ Liskov Substitution! ❖ Interface Segregation! ❖ Dependency Inversion
33. POODIR Composition describes a has-a relationship. Meals have appetizers, universities have departments, bicycles have parts. Meals, universities, and bicycles are composed objects. Appetizers, departments, and parts are roles. The composed object depends on the interface of the role.! — Sandi Metz
34. POODIR When using composition, the natural tendency is to create many small objects that contain straightforward responsibilities that are accessible through clearly defined interfaces.! ! — Sandi Metz
35. POODIR Because composed objects deal with their parts via an interface, adding a new kind of part is a simple matter of plugging in a new object that honors the interface.! ! — Sandi Metz
36. POODIR At its best, composition results in applications built of simple, pluggable objects that are easy to extend and have a high tolerance for change.! ! — Sandi Metz
37. WINNING Your design task is to recognize that a role exists, define the interface of its duck type and provide an implementation of that interface for every possible player! — Sandi Metz
38. VS
39. Data Interaction Role Role Controller Web Facade Role Role View model model
40. Takeaway ❖ Is vs Does! ❖ Context ! ❖ Roles! ❖ Smaller, Single Purpose Objects! ❖ http://orgsync.github.io/ active_interaction/
41. ❖ http://blog.cfoedge.com/2012/07/31/leveraging-cfo-expertise/! ❖ http://licensing4profits.com/leveraging-your-ip-6-step-licensing-strategy/! ❖ https://skitch-img.s3.amazonaws.com/20111231-n9qswtxgswfmmb1qq1qgj6c75y.jpg! ❖ http://bobsegarini.files.wordpress.com/2011/11/greatness-bender.jpg! ❖ http://www.disneydreaming.com/wp-content/uploads/2011/02/Special-Agent-Oso.jpg! ❖ http://en.wikipedia.org/wiki/Null_Object_pattern! ❖ http://s3.amazonaws.com/data.tumblr.com/tumblr_kvh5fd9wn31qa3b4go1_r1_1280.jpg? AWSAccessKeyId=AKIAI6WLSGT7Y3ET7ADQ&Expires=1391543515&Signature=rs%2BA45hWTH17xVq1H1G%2B3fG9rPc%3D#_=_! ❖ http://en.wikipedia.org/wiki/Facade_pattern! ❖ http://www.evergreenata.org/best-rated-toilets-for-best-life-quality/ultra-flush-toilet/! ❖ http://humourisms.com/wp-content/uploads/2012/07/Zombie-identity-crisis-908x1024.jpg! ❖ http://0.tqn.com/d/gohawaii/1/7/8/N/4/uss_bowfin_017.jpg! ❖ http://www.chaoticneutral.me/wp-content/gallery/my-chaotic-gallery/jessica-josh-06361-220x135.jpg! ❖ http://static4.businessinsider.com/image/5254342cecad044955e390c2/peyton-manning-is-about-to-destroy-tom-bradys-single- season-touchdown-record.jpg! ❖ http://upload.wikimedia.org/wikipedia/commons/1/12/Coach_Jason_Garrett.jpg! ❖ http://echidnainc.com/blog/wp-content/uploads/2013/08/custom-made.png! ❖ http://dailybunny.org/2012/12/25/bunny-will-play-the-part-of-santa-if-you-leave-out-carrots-and-apples-for-him/! ❖ http://guardianlv.com/wp-content/uploads/2014/01/man.jpg
42. ❖ http://clean-ruby.com/! ❖ http://jaoo.dk/aarhus2007/file%3Fpath%3D/2007/photos/speaker_photo/trygve_reenskaug.jpg! ❖ http://www.jayway.com/wordpress/wp-content/uploads/2009/05/Picture-883.png! ❖ http://agile2012.agilealliance.org/files/1913/3529/4063/Robert_Martin-nobull.jpg! ❖ https://s3.amazonaws.com/lonestarruby.org/sites/50974770c416420002000004/theme/images/speaker- sandi_metz.jpg! ❖ http://iheartguts.com/shop/images/medium/guts-gift-bag_med.jpg