Build Complex Domains in Rails

Rails models are simple, but your domain’s models might not be as simple as Rails would like them to be.

Modeling large, complex domains "the Rails way” can cause some serious pain. Ruby and Rails are supposed to make developers happy. Let's not allow “the Rails way” and complex domains to take the “happy” out of ruby development.

Join me as I’ll walk through a set of easy to implement Domain Driven Design (DDD) pointers. The goal is to make sure your model’s business logic stay under control no matter how complex your domain is or gets. Your application will be able to sustain steady growth and dramatically reduce business rule related defects, all the while, staying easy to grok.

I'll walk you through:

How communicating the domain properly will make an imprint on your codebase and product.
How creating boundaries around clusters of models will make your code easier to understand, manage, and interact with.
How immutable objects eliminate unnecessary complexities.
How data store access expresses the domain's intentions.
How to represent natural business transactions between models.

Transcript

1. BUILD ! COMPLEX DOMAINS! IN RAILS Mike AbiEzzi
2. BUILD ! COMPLEX DOMAINS! IN RAILS Mike AbiEzzi
4. WHAT’S A DOMAIN?
5. WHAT’S A DOMAIN?
6. WHAT’S A DOMAIN?
7. WHAT’S A DOMAIN?
8. WHY DDD?
9. WHY DDD?
10. WHY DDD?
11. WHY DDD?
12. WHY DDD?
13. WHY DDD?
14. WHY DDD?
15. WHY DDD? software becomes complex quickly
16. AIM OF THIS TALK ✘ Custom DDD architectures! ✘ DDD design patterns! ✘ Advanced DDD topics (e.g. Repository Pattern) (e.g. Bounded Context)
17. AIM OF THIS TALK ✘ Custom DDD architectures! ✘ DDD design patterns! ✘ Advanced DDD topics (e.g. Repository Pattern) (e.g. Bounded Context) custom is expensive!
18. AIM OF THIS TALK ✓ DDD principles ✓ DDD+Rails w/o a heavy investment
19. AIM OF THIS TALK ✓ DDD principles ✓ DDD+Rails w/o a heavy investment we want to hit the ground running!
20. ▾ app/! ▸ assets/! ▸ controllers/! ▸ helpers/! ▸ mailers/! ▸ models/! ▸ views/
21. 1. Defining the domain! 2. Communicating the domain! 3. Relationships between models! 4. Aggregates! 5. Data access! 6. Value Objects! 7. Domain Services
22. the domain 1
23. App Store
24. App Store brainstorm
25. App Store App brainstorm
26. Developer 1 n App Store App brainstorm
27. Developer 1 n App Store App Version 1 n brainstorm
28. Developer 1 n App Store App Version 1 n 1..6 Screenshot 1 brainstorm
29. Developer 1 n App Store Customer App Version 1 n 1..6 Screenshot 1 brainstorm
30. Developer 1 n App Store Customer App n n Purchase Version 1 n 1..6 Screenshot 1 brainstorm
31. Developer 1 n App Store Customer App Install n n n n Purchase Version 1 n 1..6 Screenshot 1 brainstorm
32. Developer 1 n App Store Customer App Install n n n n Purchase Comment 1 n n 1 Version 1 n 1..6 Screenshot 1 brainstorm
33. App Store Developer 1 n Customer App Install n n n n Purchase Comment 1 n n 1 Version 1 n 1..6 Screenshot 1 refine
34. App Store Developer 1 n Customer App Install n n n n Purchase Comment 1 n n 1 Version 1 n 1..6 Screenshot 1 Developer/ Company refine
35. App Store Developer 1 n Customer App Install n n n n Purchase Comment 1 n n 1 Version 1 n 1..6 Screenshot 1 Developer/ Company Seller refine
36. App Store Developer 1 n Customer App Install n n n n Purchase Comment 1 n n 1 Version 1 n 1..6 Screenshot 1 Release! version_number Developer/ Company Seller refine
37. App Store Developer 1 n Customer App Install n n n n Purchase Comment 1 n n 1 Review! comment! rating Version 1 n 1..6 Screenshot 1 Release! version_number Developer/ Company Seller refine
38. communication 2
39. COMMUNICATION
40. COMMUNICATION Domain! Expert
41. COMMUNICATION Domain! Expert Software! Expert
42. COMMUNICATION Domain! Expert Software! Expert brainstorm → draw diagrams → ! speak out assumptions → let them correct you → refine
43. RESPONSIBILITIES -- Eric Evans
44. RESPONSIBILITIES “Domain experts should object to terms or structures that are awkward or inadequate to convey domain understanding” -- Eric Evans
45. RESPONSIBILITIES “Domain experts should object to terms or structures that are awkward or inadequate to convey domain understanding” “Developers should watch for ambiguity or inconsistency that will trip up design.” -- Eric Evans
46. UBIQUITOUS LANGUAGE “a common, rigorous language between developers and users […] the need for it to be rigorous, since software doesn't cope well with ambiguity” — Martin Fowler
47. UBIQUITOUS LANGUAGE User “a common, rigorous language between developers and users […] the need for it to be rigorous, since software doesn't cope well with ambiguity” — Martin Fowler
48. UBIQUITOUS LANGUAGE Product! Owner User “a common, rigorous language between developers and users […] the need for it to be rigorous, since software doesn't cope well with ambiguity” — Martin Fowler
49. UBIQUITOUS LANGUAGE Domain! Expert Product! Owner User “a common, rigorous language between developers and users […] the need for it to be rigorous, since software doesn't cope well with ambiguity” — Martin Fowler
50. Tester UBIQUITOUS LANGUAGE Domain! Expert Product! Owner User “a common, rigorous language between developers and users […] the need for it to be rigorous, since software doesn't cope well with ambiguity” — Martin Fowler
51. Tester UBIQUITOUS LANGUAGE Domain! Expert Product! Owner User Designer “a common, rigorous language between developers and users […] the need for it to be rigorous, since software doesn't cope well with ambiguity” — Martin Fowler
52. Developer Tester UBIQUITOUS LANGUAGE Domain! Expert Product! Owner User Designer “a common, rigorous language between developers and users […] the need for it to be rigorous, since software doesn't cope well with ambiguity” — Martin Fowler
53. Code Developer Tester UBIQUITOUS LANGUAGE Domain! Expert Product! Owner User Designer “a common, rigorous language between developers and users […] the need for it to be rigorous, since software doesn't cope well with ambiguity” — Martin Fowler
54. Code Developer Tester UBIQUITOUS LANGUAGE Domain! Expert Product! Owner User Designer “a common, rigorous language between developers and users […] the need for it to be rigorous, since software doesn't cope well with ambiguity” — Martin Fowler Ensure one consistent language
55. relationships 3
56. App Store Developer 1 n Customer App Install n n n n Purchase Comment 1 n n 1 Review! comment! rating Version 1 n 1..6 Screenshot 1 Release! version_number Developer/ Company Seller relationships
57. App Store Developer 1 n Customer App Install n n n n Purchase Comment 1 n n 1 Review! comment! rating Version 1 n 1..6 Screenshot 1 Release! version_number Developer/ Company Seller class App < ActiveRecord::Base has_many :customers, through: :purchases ... end ! ! class Customer < ActiveRecord::Base has_many :apps, through: :purchases ... end relationships
58. App Store Developer 1 n Customer App Install n n n n Purchase Comment 1 n n 1 Review! comment! rating Version 1 n 1..6 Screenshot 1 Release! version_number Developer/ Company Seller class App < ActiveRecord::Base has_many :customers, through: :purchases ... end ! ! class Customer < ActiveRecord::Base has_many :apps, through: :purchases ... end ✓ relationships
59. App Store Developer 1 n Customer App Install n n n n Purchase Comment 1 n n 1 Review! comment! rating Version 1 n 1..6 Screenshot 1 Release! version_number Developer/ Company Seller class App < ActiveRecord::Base has_many :customers, through: :purchases ... end ! ! class Customer < ActiveRecord::Base has_many :apps, through: :purchases ... end ✓ ✘ relationships
60. App Store Developer 1 n Customer App Install n n n n Purchase Comment 1 n n 1 Review! comment! rating Version 1 n 1..6 Screenshot 1 Release! version_number Developer/ Company Seller relationships
61. 1 n App Store Developer 1 n Customer App Install n n Purchase Comment 1 n n 1 Review! comment! rating Version 1 n 1..6 Screenshot 1 Release! version_number Developer/ Company Seller relationships
62. 1 n App Store Developer 1 n Customer App Purchase Comment 1 n n 1 Review! comment! rating Version 1 n 1..6 Screenshot 1 Release! version_number Developer/ Company Seller relationships
63. 1 n App Store Developer 1 n Customer App Purchase Comment 1 n Review! comment! rating Version 1 n 1..6 Screenshot 1 Release! version_number Developer/ Company Seller relationships
64. aggregates 4
65. aggregates 4
66. release = Release.new( version_major: 1, version_minor: 1, ...) release.screenshots << [ Screenshot.new(file: "shot1.png"), Screenshot.new(file: "shot2.png")] release.status = :submitted ! app.releases << release Submit a new release of an app
67. release = Release.new( version_major: 1, version_minor: 1, ...) release.screenshots << [ Screenshot.new(file: "shot1.png"), Screenshot.new(file: "shot2.png")] release.status = :submitted ! app.releases << release Submit a new release of an app
68. release = Release.new( version_major: 1, version_minor: 1, ...) release.screenshots << [ Screenshot.new(file: "shot1.png"), Screenshot.new(file: "shot2.png")] release.status = :submitted ! app.releases << release Submit a new release of an app
69. release = Release.new( version_major: 1, version_minor: 1, ...) release.screenshots << [ Screenshot.new(file: "shot1.png"), Screenshot.new(file: "shot2.png")] release.status = :submitted ! app.releases << release Submit a new release of an app
70. release = Release.new( version_major: 1, version_minor: 1, ...) release.screenshots << [ Screenshot.new(file: "shot1.png"), Screenshot.new(file: "shot2.png")] release.status = :submitted ! app.releases << release Submit a new release of an app
71. release = Release.new( version_major: 1, version_minor: 1, ...) release.screenshots << [ Screenshot.new(file: "shot1.png"), Screenshot.new(file: "shot2.png")] release.status = :submitted ! app.releases << release A BETTER WAY? Submit a new release of an app
72. app.submit_release(“1.1.0”, screenshots: ["shot1.png", "shot2.png"]) release = Release.new( version_major: 1, version_minor: 1, ...) release.screenshots << [ Screenshot.new(file: "shot1.png"), Screenshot.new(file: "shot2.png")] release.status = :submitted ! app.releases << release A BETTER WAY? Submit a new release of an app
73. app.submit_release(“1.1.0”, screenshots: ["shot1.png", "shot2.png"]) release = Release.new( version_major: 1, version_minor: 1, ...) release.screenshots << [ Screenshot.new(file: "shot1.png"), Screenshot.new(file: "shot2.png")] release.status = :submitted ! app.releases << release A BETTER WAY? Describe domain behaviors with methods Submit a new release of an app
74. App 1 Comment 1 n Review! comment! rating n 1..6 Screenshot 1 AGGREGATE Release! version_number
75. class App < ActiveRecord::Base ... ! def submit_release ... def approve_release ... def flag_for_abuse ... ! def mark_as_staff_favorite ... ! end
76. class App < ActiveRecord::Base ... ! def submit_release ... def approve_release ... def flag_for_abuse ... ! def mark_as_staff_favorite ... ! end Tells a story of how the domain works
77. data access 5
78. Data Access App.where( "create_at > ? and purchase_count > ?", 1.week.ago, 10000).all
79. Data Access App.where( "create_at > ? and purchase_count > ?", 1.week.ago, 10000).all
80. Data Access App.where( "create_at > ? and purchase_count > ?", 1.week.ago, 10000).all require 'fig_leaf' ! class App < ActiveRecord::Base scope :new_and_noteworthy, -> { where("create_at > ? and purchases > ?", 1.week.ago, 10000) } end Use scopes
81. Data Access App.where( "create_at > ? and purchase_count > ?", 1.week.ago, 10000).all require 'fig_leaf' ! class App < ActiveRecord::Base scope :new_and_noteworthy, -> { where("create_at > ? and purchases > ?", 1.week.ago, 10000) } end Use scopes
82. Data Access App.where( "create_at > ? and purchase_count > ?", 1.week.ago, 10000).all require 'fig_leaf' ! class App < ActiveRecord::Base scope :new_and_noteworthy, -> { where("create_at > ? and purchases > ?", 1.week.ago, 10000) } end Use scopes
83. class App < ActiveRecord::Base scope :new_and_noteworthy, ... scope :staff_picks, ... scope :most_popular, ... ... ! def submit_release ... def approve_release ... ... end
84. class App < ActiveRecord::Base scope :new_and_noteworthy, ... scope :staff_picks, ... scope :most_popular, ... ... ! def submit_release ... def approve_release ... ... end One expressive point of entry
85. class App < ActiveRecord::Base scope :new_and_noteworthy, ... scope :staff_picks, ... scope :most_popular, ... ... ! def submit_release ... def approve_release ... ... end One expressive point of entry Aggregate roots are the domain’s only ! point of entry for data access.
86. ▾ app/! ▾ models/! ▾ apps/! app.rb! release.rb! review.rb! screenshot.rb! version_number.rb! ▸ customers/! ▸ sellers/
87. ▾ app/! ▾ models/! ▾ apps/! app.rb! release.rb! review.rb! screenshot.rb! version_number.rb! ▸ customers/! ▸ sellers/ Aggregate Aggregate Aggregate
88. value objects 6
89. ENTITY VALUE OBJECT
90. ENTITY VALUE OBJECT a thing
91. ENTITY VALUE OBJECT a thing describes a thing
92. ENTITY VALUE OBJECT a thing describes a thing class Customer class Name
93. ENTITY VALUE OBJECT a thing describes a thing class Customer class Name Me
 “Mike AbiEzzi”
94. ENTITY VALUE OBJECT a thing describes a thing class Customer class Name Me
 “Mike AbiEzzi” My little cousin
 “Mike AbiEzzi”
95. ENTITY VALUE OBJECT a thing describes a thing unique independent! of attributes class Customer class Name
96. ENTITY VALUE OBJECT a thing describes a thing unique independent! of attributes has a lifecycle class Customer class Name
97. ENTITY VALUE OBJECT a thing describes a thing can change state unique independent! of attributes has a lifecycle class Customer class Name
98. ENTITY VALUE OBJECT a thing describes a thing can change state unique independent! of attributes has a lifecycle class Customer class Name “Mike AbiEzzi” “Mike AbiEzzi”
99. ENTITY VALUE OBJECT a thing describes a thing can change state unique independent! of attributes immutable has a lifecycle class Customer class Name
100. ENTITY VALUE OBJECT a thing describes a thing can change state doesn’t reference anything unique independent! of attributes immutable has a lifecycle class Customer class Name
101. ENTITY VALUE OBJECT a thing describes a thing can change state doesn’t reference anything unique independent! of attributes avoids design complexities immutable has a lifecycle class Customer class Name
102. App 1 Comment 1 n Review! comment! rating n 1..6 Screenshot 1 Release! version_number What’s what?
103. App 1 Comment 1 n Review! comment! rating n 1..6 Screenshot 1 Entity Release! version_number What’s what?
104. App 1 Comment 1 n Review! comment! rating n 1..6 Screenshot 1 Entity Release! version_number Entity What’s what?
105. App 1 Comment 1 n Review! comment! rating n 1..6 Screenshot 1 Value Entity Release! version_number Entity What’s what?
106. App 1 Comment 1 n Review! comment! rating n 1..6 Screenshot 1 Value Entity Release! version_number Entity What’s what? ?
107. App 1 Comment 1 n Review! comment! rating n 1..6 Screenshot 1 Value Entity Release! version_number Entity What’s what? ? Value
108. class Screenshot attr_reader :file, :position ! def initialize(file, position) @file, @position = file, position end ! def ==(other) file == other.file && position == other.position end alias_method :eql?, :== def hash; file.hash ^ position.hash; end end VALUE OBJECT immutable / equality
109. class Screenshot attr_reader :file, :position ! def initialize(file, position) @file, @position = file, position end ! def ==(other) file == other.file && position == other.position end alias_method :eql?, :== def hash; file.hash ^ position.hash; end end VALUE OBJECT immutable / equality
110. class Screenshot attr_reader :file, :position ! def initialize(file, position) @file, @position = file, position end ! def ==(other) file == other.file && position == other.position end alias_method :eql?, :== def hash; file.hash ^ position.hash; end end VALUE OBJECT immutable / equality
111. class Screenshot attr_reader :file, :position ! def initialize(file, position) @file, @position = file, position end ! def ==(other) file == other.file && position == other.position end alias_method :eql?, :== def hash; file.hash ^ position.hash; end end VALUE OBJECT immutable / equality
112. class Screenshot attr_reader :file, :position ! def initialize(file, position) @file, @position = file, position end ! def ==(other) file == other.file && position == other.position end alias_method :eql?, :== def hash; file.hash ^ position.hash; end end VALUE OBJECT immutable / equality
113. class Screenshot attr_reader :file, :position ! def initialize(file, position) @file, @position = file, position end ! def ==(other) file == other.file && position == other.position end alias_method :eql?, :== def hash; file.hash ^ position.hash; end end VALUE OBJECT immutable / equality
114. class VersionNumber attr_reader :major, :minor, :build ... def next_major_version new VersionNumber( major + 1, minor, build) end ! def next_minor_version ... def next_build_version ... end VALUE OBJECT factory methods
115. class VersionNumber attr_reader :major, :minor, :build ... def next_major_version new VersionNumber( major + 1, minor, build) end ! def next_minor_version ... def next_build_version ... end VALUE OBJECT factory methods
116. 3 ways to persist value objects
117. 3 ways to persist value objects A. Inline on the Entity’s table
118. 3 ways to persist value objects A. Inline on the Entity’s table B. Serialized on the Entity’s table
119. 3 ways to persist value objects A. Inline on the Entity’s table B. Serialized on the Entity’s table C. In its own table
120. Release! VersionNumber! Entity Value 1 1 A. Inline on the Entity’s table releases version_major version_minor version_build …
121. A. Inline on the Entity’s table class Release < ActiveRecord::Base def version_number=(vn) @version_number = vn self[:version_major] = vn.major self[:version_minor] = vn.minor self[:version_build] = vn.build end ! def version_number @version_number ||= new VersionNumber( self[:version_major], ... ) end ! private attr_accessor :version_major, ... ! end
122. A. Inline on the Entity’s table class Release < ActiveRecord::Base def version_number=(vn) @version_number = vn self[:version_major] = vn.major self[:version_minor] = vn.minor self[:version_build] = vn.build end ! def version_number @version_number ||= new VersionNumber( self[:version_major], ... ) end ! private attr_accessor :version_major, ... ! end
123. A. Inline on the Entity’s table class Release < ActiveRecord::Base def version_number=(vn) @version_number = vn self[:version_major] = vn.major self[:version_minor] = vn.minor self[:version_build] = vn.build end ! def version_number @version_number ||= new VersionNumber( self[:version_major], ... ) end ! private attr_accessor :version_major, ... ! end
124. A. Inline on the Entity’s table class Release < ActiveRecord::Base def version_number=(vn) @version_number = vn self[:version_major] = vn.major self[:version_minor] = vn.minor self[:version_build] = vn.build end ! def version_number @version_number ||= new VersionNumber( self[:version_major], ... ) end ! private attr_accessor :version_major, ... ! end
125. Release! Screenshot! 1 1..6 B. Serialized on the Entity’s table releases … screenshots …
126. require 'oj' ! class Release < ActiveRecord::Base ! def screenshots=(screenshots) @screenshots = screenshots self[:screenshots] = Oj.dump(screenshots) end ! def screenshots @screenshots ||= Oj.load(self[:screenshots]) end ! end B. Serialized on the Entity’s table
127. require 'oj' ! class Release < ActiveRecord::Base ! def screenshots=(screenshots) @screenshots = screenshots self[:screenshots] = Oj.dump(screenshots) end ! def screenshots @screenshots ||= Oj.load(self[:screenshots]) end ! end B. Serialized on the Entity’s table
128. require 'oj' ! class Release < ActiveRecord::Base ! def screenshots=(screenshots) @screenshots = screenshots self[:screenshots] = Oj.dump(screenshots) end ! def screenshots @screenshots ||= Oj.load(self[:screenshots]) end ! end B. Serialized on the Entity’s table
129. require 'oj' ! class Release < ActiveRecord::Base ! def screenshots=(screenshots) @screenshots = screenshots self[:screenshots] = Oj.dump(screenshots) end ! def screenshots @screenshots ||= Oj.load(self[:screenshots]) end ! end B. Serialized on the Entity’s table
130. Release! Review! 1 n C. In its own table releases … reviews release_id …
131. C. In its own table class Review < ActiveRecord::Base after_save { |record| immutable!(record) } after_find { |record| immutable!(record) } ! def immutable!(record) record.readonly! attributes.each do |attr, _| record.define_singleton_method :"#{attr}=" do |_| raise "readonly" end end end ! def ==(other) ... alias_method :eql?, :== def hash ... end
132. C. In its own table class Review < ActiveRecord::Base after_save { |record| immutable!(record) } after_find { |record| immutable!(record) } ! def immutable!(record) record.readonly! attributes.each do |attr, _| record.define_singleton_method :"#{attr}=" do |_| raise "readonly" end end end ! def ==(other) ... alias_method :eql?, :== def hash ... end
133. C. In its own table class Review < ActiveRecord::Base after_save { |record| immutable!(record) } after_find { |record| immutable!(record) } ! def immutable!(record) record.readonly! attributes.each do |attr, _| record.define_singleton_method :"#{attr}=" do |_| raise "readonly" end end end ! def ==(other) ... alias_method :eql?, :== def hash ... end
134. C. In its own table class Review < ActiveRecord::Base after_save { |record| immutable!(record) } after_find { |record| immutable!(record) } ! def immutable!(record) record.readonly! attributes.each do |attr, _| record.define_singleton_method :"#{attr}=" do |_| raise "readonly" end end end ! def ==(other) ... alias_method :eql?, :== def hash ... end
135. C. In its own table class Review < ActiveRecord::Base after_save { |record| immutable!(record) } after_find { |record| immutable!(record) } ! def immutable!(record) record.readonly! attributes.each do |attr, _| record.define_singleton_method :"#{attr}=" do |_| raise "readonly" end end end ! def ==(other) ... alias_method :eql?, :== def hash ... end
136. C. In its own table class Review < ActiveRecord::Base after_save { |record| immutable!(record) } after_find { |record| immutable!(record) } ! def immutable!(record) record.readonly! attributes.each do |attr, _| record.define_singleton_method :"#{attr}=" do |_| raise "readonly" end end end ! def ==(other) ... alias_method :eql?, :== def hash ... end
137. C. In its own table class Review < ActiveRecord::Base after_save { |record| immutable!(record) } after_find { |record| immutable!(record) } ! def immutable!(record) record.readonly! attributes.each do |attr, _| record.define_singleton_method :"#{attr}=" do |_| raise "readonly" end end end ! def ==(other) ... alias_method :eql?, :== def hash ... end
138. domain services 7
139. Gift an App SERVICE
140. Gift an App SERVICE 1. Charge the gifter that’s purchasing the app.
141. Gift an App SERVICE 1. Charge the gifter that’s purchasing the app. 2. Assign access rights to the giftee receiving the app.
142. Gift an App SERVICE 1. Charge the gifter that’s purchasing the app. 2. Assign access rights to the giftee receiving the app. Facilitates a transaction between two aggregates
143. Purchase 1 n Customer
144. Purchase 1 n Customer AccessRight 1 n
145. class GiftApp def self.execute(app, gifter, giftee) Purchase.create( app: app, customer: gifter, ...) AccessRight.create( app: app, customer: giftee, purchase: purchase, ...) end end Purchase 1 n Customer AccessRight 1 n
146. class GiftApp def self.execute(app, gifter, giftee) Purchase.create( app: app, customer: gifter, ...) AccessRight.create( app: app, customer: giftee, purchase: purchase, ...) end end Purchase 1 n Customer AccessRight 1 n
147. class GiftApp def self.execute(app, gifter, giftee) Purchase.create( app: app, customer: gifter, ...) AccessRight.create( app: app, customer: giftee, purchase: purchase, ...) end end Purchase 1 n Customer AccessRight 1 n
148. class GiftApp def self.execute(app, gifter, giftee) Purchase.create( app: app, customer: gifter, ...) AccessRight.create( app: app, customer: giftee, purchase: purchase, ...) end end Purchase 1 n Customer AccessRight 1 n
149. class GiftApp def self.execute(app, gifter, giftee) Purchase.create( app: app, customer: gifter, ...) AccessRight.create( app: app, customer: giftee, purchase: purchase, ...) end end Purchase 1 n Customer AccessRight 1 n
150. ▾ app/! ▸ models/! ▾ services/! gift_app.rb! refund_purchase.rb! purchase_app.rb! ...
151. IN SUMMARY
152. Continuously refine the domain with a domain expert 1
153. Insist on having a ubiquitous language for seamless communication 2
154. Constrain relationships to only what the domain needs 3
155. Create aggregates that express domain concepts and manage complexity 4
156. Express the domain’s intent through! well defined data access 5
157. Create value objects to eliminate unnecessary complexity 6
158. Create domain services to express transactions ! between aggregates 7
159. ▾ app/! ▸ assets/! ▸ controllers/! ▸ helpers/! ▸ mailers/! ▸ models/! ▸ views/
160. ▾ app/! ▾ models/! ▸ apps/! app.rb! ...! ▸ customers/! ▸ sellers/! ▸ ...! ▸ services/! gift_app.rb! refund_purchase.rb! ...
161. ▾ app/! ▾ models/! ▸ apps/! app.rb! ...! ▸ customers/! ▸ sellers/! ▸ ...! ▸ services/! gift_app.rb! refund_purchase.rb! ... aggregates
162. ▾ app/! ▾ models/! ▸ apps/! app.rb! ...! ▸ customers/! ▸ sellers/! ▸ ...! ▸ services/! gift_app.rb! refund_purchase.rb! ... aggregates entry point to domain behaviors & ! data retrieval
163. ▾ app/! ▾ models/! ▸ apps/! app.rb! ...! ▸ customers/! ▸ sellers/! ▸ ...! ▸ services/! gift_app.rb! refund_purchase.rb! ... aggregates cross aggregate transactions entry point to domain behaviors & ! data retrieval
164. Thanks for Listening!
165. Thanks for Listening! We’re hiring!
166. Thanks for Listening! www.virtual-genius.com Special thanks to We’re hiring!
167. @mjezzi www.mikeabiezzi.com
168. @mjezzi www.mikeabiezzi.com /#mentorship