Domain-Driven Design - True North PHP 2016

Transcript

1. Domain-driven
   Design
   Deconstructed
   Domain-driven
   Design
   Deconstructed
   Andrew Cassell
   

   View Slide

2. View Slide

3. View Slide

4. View Slide

5. View Slide

6. View Slide

7. Domain-Driven
   Design
   

   View Slide

8. View Slide

9. View Slide

10. View Slide

11. View Slide

12. Domain-Driven
    Design
    

    View Slide

13. DDD
    

    View Slide

14. View Slide

15. View Slide

16. View Slide

17. View Slide

18. View Slide

19. People don't want to buy a quarter-inch
    drill, they want a quarter-inch hole.
    Theodore Levitt
    

    View Slide

20. Domain
    

    View Slide

21. Domain
    

    View Slide

22. Penn State Pattee Library
    

    View Slide

23. book
    user
    book_inventory
    book_inventory_user_link
    ROLE_USER
    ROLE_ADMIN
    

    View Slide

24. Source: http://jonclaytonbiz.com/
    

    View Slide

25. View Slide

26. #DDD4ME
    

    View Slide

27. View Slide

28. View Slide

29. View Slide

30. View Slide

31. Common Sense
    Software
    Development
    

    View Slide

32. http://www.sei.cmu.edu/reports/95tr021.pdf
    

    View Slide

33. View Slide

34. DDD BALL OF MUD/CRUD
    Correctness
    Testability
    Usability
    Maintainability
    Modifiability
    

    View Slide

35. Performance
    

    View Slide

36. View Slide

37. Security
    

    View Slide

38. DDD Common
    Misconceptions
    

    View Slide

39. View Slide

40. View Slide

41. View Slide

42. View Slide

43. View Slide

44. View Slide

45. View Slide

46. CRUD is okay-ish
    

    View Slide

47. View Slide

48. View Slide

49. View Slide

50. View Slide

51. Ubiquitous
    Language
    

    View Slide

52. Ubiquitous Language
    Developers
    Domain
    Experts
    

    View Slide

53. View Slide

54. View Slide

55. Ubiquitous
    Language
    

    View Slide

56. User
    Customer
    Client
    Member
    Affiliate
    

    View Slide

57. 1. Naming Things
    2. Cache Invalidation
    3. Off By One Errors
    Top 10 Reasons
    Programming is Hard
    

    View Slide

58. DDD CRUD/MUD
    Members Users
    LibraryCatalog BookRepository
    ISBN String
    DeweyDecimal Float(7,3)
    

    View Slide

59. $user = User::findOrFail($uuid);

    $book = Books::where('isbn', '=', $isbn)->take(1)->get();

    

    

    if (!$user->userBookLinks()->contains($book->id) && $user->borrowLinks->count() < 5) {

    

    $user->userBookLinks()->attach($book->id, ['date_due' => new DateTime('+2 Weeks')];

    

    }

    

    

    $user->save();
    

    View Slide

60. View Slide

61. $catalog = new LibraryCatalog(…);
    $book = $catalog->findOneBookByISBN($isbn);
    $members = new Members(…);
    $borrower = $members->findOneByAccountNumber($id);
    $borrower->borrow($book);
    $members->updateAccount($borrower);
    

    View Slide

62. $borrower->borrow($book);
    $borrower->loan($book);
    $borrower->obtain($book);
    $borrower->take($book);
    

    View Slide

63. DDD BALL OF MUD/CRUD
    Correctness ✓
    Testability
    Usability
    Maintainability
    Modifiability
    

    View Slide

64. View Slide

65. View Slide

66. Sales
    Marketing
    Finance
    Production
    

    View Slide

67. Customer
    Lead
    Payee
    ShipTo
    

    View Slide

68. Slide: Vaughn Vernon
    

    View Slide

69. View Slide

70. View Slide

71. View Slide

72. Alberto Brandolini
    

    View Slide

73. http://ziobrando.blogspot.be/
    

    View Slide

74. View Slide

75. View Slide

76. View Slide

77. View Slide

78. View Slide

79. View Slide

80. 7 Dirty Words When Meeting With a Domain Expert
    1.Session
    2.Repository
    3.Abstract
    4.Interface
    5.Class
    6.Database
    7.Foreign Key
    

    View Slide

81. View Slide

82. View Slide

83. User Research
    

    View Slide

84. Photo: Mathias Verraes
    

    View Slide

85. View Slide

86. View Slide

87. View Slide

88. View Slide

89. View Slide

90. View Slide

91. View Slide

92. View Slide

93. View Slide

94. View Slide

95. View Slide

96. View Slide

97. Domain Objects
    Repositories
    Commands & Command handlers
    Business rules/specifications
    Messages
    Domain events
    

    Aggregates
    Entities
    Value Objects
    Invariants
    Processes
    

    View Slide

98. Domain Objects
    Repositories
    Commands & Command handlers
    Business Rules/Specifications
    Messages
    Domain Events
    

    Aggregates
    Entities
    Value Objects
    Invariants
    Processes
    

    View Slide

99. Value Object
    Immutable
    No Identity (Only Values)
    Entity
    Mutable
    Has A Lifecycle
    Always Stable
    Contains Value Objects
    Aggregate
    Entity
    Responsible For Child Entities
    

    View Slide

100. Value Objects
     Amount Paid
     Email Address
     BookTitle
     Dewey Decimal Number
     ISBN Number
     

     View Slide

101. Immutability
     Avoid Spooky
     Action at a
     Distance
     

     View Slide

102. Value Objects
     

     View Slide

103. Not Just Static Typing
     https://github.com/Fiedzia/type-system-research/blob/master/README.md
     Value Objects
     

     View Slide

104. “Gateway Drug to
     Test Driven Development”
     Value Objects
     

     View Slide

105. “Gateway Drug to
     Test Driven Development”
     Value Objects
     #MYTESTSDONTPASS
     

     View Slide

106. Value Objects
     ALWAYS IN A
     VALID STATE
     

     View Slide

107. Plain PHP Objects (POPOs)
     •Declare Class Properties as Private
     •No Setters
     •All Parameters Are Injected in the Constructor
     •Do Not Store References to Mutable Objects (Private Scalars Okay)
     •Throw Exceptions If Something Is Wrong
     •Functions that Appear to Modify Should Return a New Object
     •Declare the Class Final so it can’t be Overridden (probably)
     Value Objects
     

     View Slide

108. Example
     BookTitle
     

     View Slide

109. View Slide

110. View Slide

111. View Slide

112. View Slide

113. View Slide

114. View Slide

115. View Slide

116. Example
     BookCondition
     

     View Slide

117. View Slide

118. View Slide

119. View Slide

120. View Slide

121. Example
     DateBorrowed
     

     View Slide

122. View Slide

123. Example
     DateDue
     

     View Slide

124. View Slide

125. Example
     LoanPeriod
     

     View Slide

126. View Slide

127. DDD CRUD/MUD
     BookTitle String
     BookCondition String
     ISBN String
     DeweyDecimal Float(7,3)
     DateBorrowed DateTime
     

     View Slide

128. DDD BALL OF MUD/CRUD
     Correctness ✓
     Testability ✓
     Usability
     Maintainability
     Modifiability
     

     View Slide

129. View Slide

130. Identifiable
     Has State and is Mutable
     Never Invalid State
     Required Parameters Passed in Constructor
     Operates Using Value Objects
     No Security or Permission Checks
     Storage Agnostic
     Entities
     

     View Slide

131. Entities
     Librarian
     Book
     

     View Slide

132. View Slide

133. View Slide

134. SETTERS
     ARE BAD
     

     View Slide

135. View Slide

136. View Slide

137. View Slide

138. View Slide

139. View Slide

140. View Slide

141. Doctrine
     

     View Slide

142. View Slide

143. •Special Kind of Entity
     •Manages Child Entities
     •Transactionally Safe
     Aggregates
     

     View Slide

144. Aggregates
     Member
     Fines Invoice
     

     View Slide

145. View Slide

146. View Slide

147. View Slide

148. View Slide

149. View Slide

150. Task Based
     User Interface
     

     View Slide

151. View Slide

152. View Slide

153. DDD BALL OF MUD/CRUD
     Correctness ✓
     Testability ✓
     Usability ✓
     Maintainability
     Modifiability
     

     View Slide

154. Security
     

     View Slide

155. Domain
     (Business Logic)
     Application
     Services
     Controller
     Persistence
     Event/Command Bus
     Security
     Templates
     

     View Slide

156. Controller
     Domain
     Framework
     

     View Slide

157. View Slide

158. View Slide

159. View Slide

160. View Slide

161. Controller
     Domain
     Framework
     

     View Slide

162. Mathias Verraes - Decoupling the Model from the Framework at Laracon EU 2014
     https://www.youtube.com/watch?v=QaIGN_cTcc8
     

     View Slide

163. Ruby Midwest 2011 - Keynote: Architecture the Lost Years by Robert Martin
     https://www.youtube.com/watch?v=WpkDN78P884
     

     View Slide

164. Domain
     (Business Logic)
     Application
     Services
     Controller
     Persistence
     Event/Command Bus
     Security
     Templates
     

     View Slide

165. DDD BALL OF MUD/CRUD
     Correctness ✓
     Testability ✓
     Usability ✓
     Maintainability ✓
     Modifiability
     

     View Slide

166. Domain
     Events
     

     View Slide

167. Domain Events
     •Something That Happened In The Past
     •Immutable Value Objects
     •Part of the Core Domain
     •Usually Created in an Aggregate
     •Probably Want To Persist Them
     •Passed to Event Bus (Application Layer)
     •Listeners are Application Services
     •Used To Cross Bounded Contexts
     •Do Not Contain Entities (Only Value Objects)
     

     View Slide

168. View Slide

169. View Slide

170. View Slide

171. BookWasOverdue
     

     View Slide

172. View Slide

173. DDD BALL OF MUD/CRUD
     Correctness ✓
     Testability ✓
     Usability ✓
     Maintainability ✓
     Modifiability ✓
     

     View Slide

174. Command Query
     Responsibility
     Segregation
     

     View Slide

175. CQRS
     

     View Slide

176. Slide: Microsoft
     

     View Slide

177. View Slide

178. View Slide

179. View Slide

180. View Slide

181. https://gnugat.github.io/
     2016/05/11/towards-cqrs-
     command-bus.html
     

     View Slide

182. View Slide

183. View Slide

184. View Slide

185. Controller
     Domain
     Framework
     

     View Slide

186. Event
     Sourcing
     

     View Slide

187. Event Sourcing
     •Store the Events That Happen
     •Append Only Event Storage
     •Object Properties are Not Stored
     

     View Slide

188. View Slide

189. View Slide

190. View Slide

191. Event Sourcing
     •Avoids Data Mapping
     •Avoids Object-relational Impedance Mismatch
     •Reduces Database Table Counts (Related Tables)
     •Potentially Reduces Model Counts
     

     View Slide

192. Slide: Microsoft
     

     View Slide

193. View Slide

194. View Slide

195. View Slide

196. Libraries
     •https://github.com/szjani/predaddy
     •https://github.com/prooph
     •https://github.com/qandidate-labs/broadway
     

     View Slide

197. Learning
     More
     

     View Slide

198. View Slide

199. DevBookClub
     https://www.youtube.com/user/devbookclub
     

     View Slide

200. View Slide

201. View Slide

202. View Slide

203. View Slide

204. View Slide

205. DDDinPHP
     Google Group
     http://DDDinPHP.org
     

     View Slide

206. View Slide

207. View Slide

208. Manage Private Internal
     Dependencies With
     Composer and Satis
     

     View Slide

209. https://joind.in/talk/82ad0
     Topics Covered
     •Ubiquitous Language
     •Event Storming
     •Modelling
     •Value Objects
     •Entities
     •Aggregates
     •Hexagonal Architecture
     •CQRS
     •Event Sourcing
     

     View Slide