My domain is mine and I don't share it

What's business logic exactly? What's a domain model? Which truths hide behind "patterns" like fat model - skinny controller? How does the use of a framework like Rails influence how we build a domain model?

This talk will approach the problems that we have to face when we put a tool in the core of our system and we will discuss whether the price we pay for the rails is too high.

This talk was given on Madrid.rb users group.

Transcript

1. My Domain is Mine jacegu jacegu javieracero.com and I don’t share it !!
2. once upon a time...
3. there was a keynote
4. ARCHITECTURE the lost years Robert Martin / Uncle Bob
5. ARCHITECTURE “WEB” IS NOT AN
6. IS DELIVERED “WEB” IS HOW YOUR APP
7. ARCHITECTURE FRAMEWORKS IS NOT ABOUT
8. ARCHITECTURE DEFERRING IS ABOUT DECISIONS
9. FRAMEWORKS A DETAIL ARE JUST
10. RAILS IS A DETAIL
11. RAILS IS NOT YOUR APP
12. RAILS IS NOT A WAY
16. wait a minute...
17. WTF DOES THAT EVEN MEAN ???????????????????????? ???????????????????????? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
18. let’s think it through
19. jacegu jacegu javieracero.com
24. PRESENTATION BUSINESS LOGIC DATA SOURCES 1 2 3
25. ARE THESE 3 LAYERS YOUR APP? ARE THEY EQUALLY IMPORTANT? DO THEY OBEY THE SAME RULES? DO THEY CHANGE AT THE SAME PACE?
26. ARE THESE 3 LAYERS YOUR APP? ARE THEY EQUALLY IMPORTANT? DO THEY OBEY THE SAME RULES? DO THEY CHANGE AT THE SAME PACE?
27. ARE THESE 3 LAYERS YOUR APP? ARE THEY EQUALLY IMPORTANT? DO WE BUILD THEM THE SAME WAY? DO THEY CHANGE AT THE SAME PACE?
28. ARE THESE 3 LAYERS YOUR APP? ARE THEY EQUALLY IMPORTANT? DO WE BUILD THEM THE SAME WAY? DO THEY CHANGE AT THE SAME PACE?
29. HOW OFTEN DO BUSINESS RULES CHANGE
30. HOW OFTEN DO DOMAIN RULES CHANGE
31. HOW OFTEN DO NAMING RULES CHANGE
32. IT’S ALL ABOUT CHANGE
33. BUSINESS is a DIFFERENT LOGIC KIND OF BEAST
34. ???????????????????????? ???????????????????????? ? ? ? ? ? ? ? ? ? ? ? ? ? ? what’s business logic
35. IKIPEDI W A
36. Business logic is a non-technical term used to describe the functional algorithms that handle information exchange between a database and a user interface - WIKIPEDIA
37. Business logic is a non-technical term used to describe the functional algorithms that handle information exchange between a database and a user interface - WIKIPEDIA
38. LET’S ASK @DHH
39. LET’S ASK @DHH http://37signals.com/svn/posts/3375-the-five-programming-books-that-meant-most-to-me
43. Business logic is the work the application needs to do for the domain it’s working with - Martin Fowler - Patterns of Enterprise Application Architecture
44. CALCULATIONS VALIDATIONS CALLS TO OTHER SYSTEMS BUSINESS LOGIC
45. yep, sure, but... how does it look like ???????????????????????? ???????????????????????? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
46. MORE PEAA
47. TRANSACTION SCRIPT
48. TRANSACTIONS business logic as
49. PROCEDURES modeled as def new_purchase DB.insert(data) DB.commit; end
50. simple easy to understand works great with simple datasources makes transaction boundaries visible 00 {ADVANTAGES
51. DIS 00 {duplicated code procedural code duplicated code procedural code duplicated code procedural code duplicated code procedural code ADVANTAGES
52. duplicated code gets worse as the application grows time
53. TABLE MODULE
54. OPERATIONS business logic as TABLE ROWS on
55. OBJECTS modeled as class Product def purchase recordSet.save RECORD SETS & class RecordSet
56. helps overcoming the relational - o.o. mismatch avoids duplication better than a transaction script 00 {ADVANTAGES
57. 00 {modeling limited by and tied to the data model mechanisms basic to oop like polymorphism are not available DISADVANTAGES
58. DOMAIN MODEL
59. A software model based specifically in the domain of the business you are working with. - Vaughn Vernon - Implementing Domain Driven Design
60. It’s usually built as an object model, where objects have both data and behaviour with accurate business meaning. - Vaughn Vernon - Implementing Domain Driven Design
61. OBJECT business logic as BEHAVIOUR
62. OBJECT GRAPHS modeled as Product Price Stock ProductService ProductRepository
63. The Object Oriented way of implementing business logic. - Martin Fowler - Patterns of Enterprise Application Architecture
64. - Martin Fowler - Patterns of Enterprise Application Architecture Using a Domain Model as opposed to a Transaction Script is the essence of the paradigm shift to Object Oriented programming.
65. The Object Oriented way of implementing business logic. ADVANTAGES
66. the hardest to comprehend data sources get more complex overhead for simple business logic DISADVANTAGES 00 {
67. which one should I use? ???????????????????????? ???????????????????????? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
68. effort to enhance complexity of the business logic domain model table module transaction script
69. 7.42 effort to enhance complexity of the business logic domain model table module transaction script
70. dude... get to the point!
71. HOW DOES “BUSINESS LOGIC ON RAILS” LOOK LIKE
72. probably a “domain model”
73. PROGRAMMING IS HARD
74. DESIGN IS EVEN HARDER
75. IMPLEMENTING A DOMAIN MODEL IS NOT EASY
76. antipatterns
77. ANEMIC DOMAIN MODEL
78. OBJECTS HAVE NO BEHAVIOUR
79. BUSINESS LOGIC IS SOMEWHERE ELSE
80. IN CONTROLLERS IN SERVICES so-called
81. J2EE WAY?
82. J2EE WAY? transaction script
83. SKINNY CONTROLLER FAT MODEL http://weblog.jamisbuck.org/2006/10/18/skinny-controller-fat-model
84. Controller Model
85. Controller Model THE PIPE REFACTOR
86. Controller Model http://joncairns.com/2013/04/fat-model-skinny-controller-is-a-load-of-rubbish/ this won’t create a domain model
87. Controller Model http://joncairns.com/2013/04/fat-model-skinny-controller-is-a-load-of-rubbish/ this is just turning a transaction script upside down
88. DESIGN PATTERN “PUSH IT DOWN” IS NOT A
89. Controller Model
90. Controller Model
91. Controller Model look! a god object
92. do not worry pal... rails has a way to tackle that! CONCERNS
96. RUBY IS DYNAMIC IN NATURE
98. SAME COMPLEXITY SAME L O C COUNT or even bigger! . . . http://www.slideshare.net/pcalcado/from-a-monolithic-ruby-on-rails-app-to-the-jvm
99. CONCERNS ARE A TEXT EDITOR FEATURE
100. INHERITANCE MIXINS CONCERNS
101. MULTIPLE INHERITANCE MIXINS CONCERNS
102. INHERITANCE IS THE STRONGEST FORM OF COUPLING
103. http://www.midmarsh.co.uk/planetjava/tutorials/design/InheritanceConsideredHarmful.PDF CONSIDERED HARMFUL INHERITANCE
104. http://www.artima.com/weblogs/viewpost.jsp?thread=246341 CONSIDERED HARMFUL MIXINS
105. TABLE DRIVEN DOMAIN MODEL
106. WHEN THE DOMAIN MODEL IS A DATA MODEL
107. :Payment EVERY DOMAIN OBJECT HAS A TABLE BEHIND IT :Product :Purchase
108. Another argument against ActiveRecord is the fact that it couples the object design to the database design. This makes difficult to refactor either design as the project goes forward. - Martin Fowler - Patterns of Enterprise Application Architecture
109. ACTIVE RECORD
110. ACTIVE RECORD GuILTY http://railsoopbook.com
112. DATABASES A HARDWARE SOLVE PROBLEM
113. DATA SOURCES 3 databases belong in here
114. databases belong in here BUSINESS LOGIC 2 do not
115. CRUD OBSESSION the
116. Active Record is a good choice for business logic that is not too complex, such as creates, reads updates and deletes - Martin Fowler - Patterns of Enterprise Application Architecture
117. Creates Deletes Reads Updates
118. Database Database Database Database
119. } Creates Deletes Reads Updates are consequences of use cases not use casesthemselves
120. we are not digitalizing paper anymore
121. there is an app for that
122. DOMAIN MODEL CONNECTED
123. a. k. a. RAILS WAY’S DOMAIN MODEL THE
124. a. k. a. FRAMEWORK DOMAIN MODEL THE
125. a. k. a. CONNECTED DESIGN DOMAIN MODEL THE
126. a. k. a. ARCHITECTURELESS DOMAIN MODEL THE
127. a. k. a. RAILS IS YOUR APP DOMAIN MODEL THE
128. NO LAYERING
129. NO SEPARATION OF PRESENTATION BUSINESS LOGIC DATA SOURCES 1 2 3
131. STATE GL BAL
132. business logic context it’s running in <<depends on>>
133. http://permalink.gmane.org/gmane.comp.programming.goos/1895 An object whose design depends on its persistence mechanism: context dependent. Painful. - J. B. Rainsberger - On the GOOS Mailing List
134. http://michaelfeathers.typepad.com/michael_feathers_blog/2013/01/the-framework-superclass-anti-pattern.html When you inherit code from a framework, it is mixed with your logic. Often you are obliged to run that inherited code with the code that you really want to test, along with all of its dependencies, start up time... - Michael Feathers - On his blog on January 2013
135. http://michaelfeathers.typepad.com/michael_feathers_blog/2013/01/the-framework-superclass-anti-pattern.html If you've written logic important to your domain, there is nothing preventing you from being able to use that logic with other technology - nothing except coupling. - Michael Feathers - On his blog on January 2013
136. ACTIVE RECORD
137. ACTIVE RECORD GuILTY http://railsoopbook.com http://www.slideshare.net/pcalcado/from-a-monolithic-ruby-on-rails-app-to-the-jvm
138. “rails is not your app” what means is...
139. YOUR APP IS YOUR BUSINESS LOGIC
140. MAKE IT CONTEXT INDEPENDENT
141. MAKE IT DELIVERY INDEPENDENT
142. MAKE IT FRAMEWORK INDEPENDENT
143. wrapping up
144. what about productivity?
146. http://www.threeriversinstitute.org/blog/?p=338 In a connected system, elements are highly available to each other. Adding the first feature to a connected system is cheap. All the resources you need are available. However, the cost of all those connections is that subsequent features are very likely to interact with previous features, driving up the cost of development over time.
147. http://www.threeriversinstitute.org/blog/?p=338 In a modular design connections are deliberately kept to a minimum. The cost for the first feature is likely to be higher than in the connected system, because you need to find the necessary resources and bring them together, possibly re-modularizing in the process. Features are much less likely to interact in a modular system, though, leading to a steady stream of features at relatively constant cost.
148. THE RAILS WAY IS A TRADEOFF
149. THE RAILS WAY IS A TRADEOFF a really big one!
150. finally...
151. - Not about anemic domain models - Nothing to do with J2EE - Also on @DHH’s list (ironically) - The rails way’s antithesis (IMHO) - Not about data centric approaches - Not on @DHH’s list (but it should)
152. RAILS VS CONTEXT INDEPENDENCE RAILS VS MODULAR DESIGN RAILS VS OOP
153. RAILS VS CONTEXT INDEPENDENCE RAILS VS MODULAR DESIGN RAILS VS OOP do not care about this
154. RAILS VS CONTEXT INDEPENDENCE RAILS VS MODULAR DESIGN RAILS VS OOP do not care about this
155. CONNECTED DESIGN VS MODULAR DESIGN
156. CONTEXT DEPENDENCE VS CONTEXT INDEPENDENCE
157. FRAMEWORKS ARE NOT WAYS OF LIFE JUST TOOLS http://blog.8thlight.com/uncle-bob/2011/09/30/Screaming-Architecture.html
158. now beer! thank you
159. Credits
160. Ruby Midwest 2011 Logo: http://cdn.confreaks.com/system/events/logos/49/rmw-logo-mid-original.png?1323836412 Uncle Bob picture: http://www.flickr.com/photos/koss/3250213001/ Home Alone Picture: http://www.multiplemayhemmamma.com/wp-content/uploads/2013/03/home-alone.jpg Terrified Adult Picture: http://sidoxia.files.wordpress.com/2011/02/scared.jpg Terrified Baby Picture: http://2.bp.blogspot.com/_0p-Jm7tsSa8/TNDUaU-HdHI/AAAAAAAAFfE/9ubR079H9UE/s1600/DSC_0425.JPG Spaghetti Picture: http://tonispilsburycom.wpengine.netdna-cdn.com/wp-content/uploads/2012/01/Mira10.jpg Dr. House Picture: http://4.bp.blogspot.com/-_EO0zOLq8YU/T8OUH5Zl5rI/AAAAAAAABLk/O_LYbtJuS1w/s1600/House+facepalm.jpg Martin Fowler Picture: http://www.flickr.com/photos/pragdave/173640462/ Vaughn Vernon Picture: https://si0.twimg.com/profile_images/1670662520/VaughnVernon_2011_2.JPG Fat & Skinny Silhouette: http://2.bp.blogspot.com/-C_B_KLHbBJ4/TiMWn5L5xUI/AAAAAAAAEDs/lqwnKydRPiQ/s1600/transition-fat_to_thin1.jpg Bear Facepalm Picture: http://blog.littlebigfund.org/wp-content/uploads/2013/04/facepalm-wallpaper.jpg Lion Facepalm Picture: http://wolfallen.w.o.pic.centerblog.net/nqgyh2l0.jpg
161. Table Icon: http://fortawesome.github.io/Font-Awesome/icon/table/ Robot: http://icons.iconarchive.com/icons/martin-berube/character/256/Robot-icon.png Monster: http://icons.iconarchive.com/icons/martin-berube/character/256/Monster-icon.png Database Icon: http://iconmonstr.com/database-icon/ Buried In Paper Picture: http://everythingchangesbook.com/wp-content/uploads/2009/03/paper-pile.jpg Cave Picture: http://imagenes.viajeros.com/fotos/l/ll/lleimrlh-1259512525.jpg Globe Icon: http://iconmonstr.com/globe-4-icon/ Refresh Icon: http://iconmonstr.com/refresh-2-icon/ J.B. Rainsberger Avatar: http://www.devtraining.ee/sites/default/files/trainers/rainsberger_0.jpg Michael Feathers Avatar: http://i985.photobucket.com/albums/ae335/edepodesta/MichaelFeathersNew.jpg Kent Beck Picture: http://www.flickr.com/photos/26420411@N02/3062930943/ Tool Icon: http://fortawesome.github.io/Font-Awesome/icon/wrench/