Domain-Driven Design - True North PHP 2016

Transcript

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

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7. Domain-Driven Design

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12. Domain-Driven Design

13. DDD

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

    a quarter-inch hole. Theodore Levitt

20. Domain

21. Domain

22. Penn State Pattee Library

23. book user book_inventory book_inventory_user_link ROLE_USER ROLE_ADMIN

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

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26. #DDD4ME

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31. Common Sense Software Development

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

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

35. Performance

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37. Security

38. DDD Common Misconceptions

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46. CRUD is okay-ish

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51. Ubiquitous Language

52. Ubiquitous Language Developers Domain Experts

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55. Ubiquitous Language

56. User Customer Client Member Affiliate

57. 1. Naming Things 2. Cache Invalidation 3. Off By One

    Errors Top 10 Reasons Programming is Hard

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

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();
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61. $catalog = new LibraryCatalog(…); $book = $catalog->findOneBookByISBN($isbn); $members = new

    Members(…); $borrower = $members->findOneByAccountNumber($id); $borrower->borrow($book); $members->updateAccount($borrower);

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

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

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66. Sales Marketing Finance Production

67. Customer Lead Payee ShipTo

68. Slide: Vaughn Vernon

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72. Alberto Brandolini

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

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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
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83. User Research

84. Photo: Mathias Verraes

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

    Domain events 
 Aggregates Entities Value Objects Invariants Processes

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

    Domain Events 
 Aggregates Entities Value Objects Invariants Processes

99. Value Object Immutable No Identity (Only Values) Entity Mutable Has

    A Lifecycle Always Stable Contains Value Objects Aggregate Entity Responsible For Child Entities

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

     ISBN Number

101. Immutability Avoid Spooky Action at a Distance

102. Value Objects

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

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

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

106. Value Objects ALWAYS IN A VALID STATE

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

108. Example BookTitle

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116. Example BookCondition

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121. Example DateBorrowed

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123. Example DateDue

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125. Example LoanPeriod

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

     DateBorrowed DateTime

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

     Modifiability
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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

131. Entities Librarian Book

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134. SETTERS ARE BAD

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141. Doctrine

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

144. Aggregates Member Fines Invoice

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150. Task Based User Interface

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

     Maintainability Modifiability

154. Security

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

     Templates

156. Controller Domain Framework

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161. Controller Domain Framework

162. Mathias Verraes - Decoupling the Model from the Framework at

     Laracon EU 2014 https://www.youtube.com/watch?v=QaIGN_cTcc8

163. Ruby Midwest 2011 - Keynote: Architecture the Lost Years by

     Robert Martin https://www.youtube.com/watch?v=WpkDN78P884

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

     Templates

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

     Maintainability ✓ Modifiability

166. Domain Events

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)
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171. BookWasOverdue

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

     Maintainability ✓ Modifiability ✓

174. Command Query Responsibility Segregation

175. CQRS

176. Slide: Microsoft

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

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185. Controller Domain Framework

186. Event Sourcing

187. Event Sourcing •Store the Events That Happen •Append Only Event

     Storage •Object Properties are Not Stored
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191. Event Sourcing •Avoids Data Mapping •Avoids Object-relational Impedance Mismatch •Reduces

     Database Table Counts (Related Tables) •Potentially Reduces Model Counts

192. Slide: Microsoft

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

197. Learning More

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

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

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208. Manage Private Internal Dependencies With Composer and Satis

209. https://joind.in/talk/82ad0 Topics Covered •Ubiquitous Language •Event Storming •Modelling •Value Objects

     •Entities •Aggregates •Hexagonal Architecture •CQRS •Event Sourcing