Domain-Driven Design - True North PHP 2016

Transcript

1. Domain-driven Design Deconstructed Domain-driven Design Deconstructed Andrew Cassell
7. Domain-Driven Design
12. Domain-Driven Design
13. DDD
17. 18
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/
26. #DDD4ME
31. Common Sense Software Development
32. http://www.sei.cmu.edu/reports/95tr021.pdf
34. DDD BALL OF MUD/CRUD Correctness Testability Usability Maintainability Modifiability
35. Performance
37. Security
38. DDD Common Misconceptions
46. CRUD is okay-ish
51. Ubiquitous Language
52. Ubiquitous Language Developers Domain Experts
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();
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
66. Sales Marketing Finance Production
67. Customer Lead Payee ShipTo
68. Slide: Vaughn Vernon
72. Alberto Brandolini
73. http://ziobrando.blogspot.be/
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
83. User Research
84. Photo: Mathias Verraes
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
116. Example BookCondition
121. Example DateBorrowed
123. Example DateDue
125. Example LoanPeriod
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
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
134. SETTERS ARE BAD
141. Doctrine
143. •Special Kind of Entity •Manages Child Entities •Transactionally Safe Aggregates
144. Aggregates Member Fines Invoice
150. Task Based User Interface
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
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)
171. BookWasOverdue
173. DDD BALL OF MUD/CRUD Correctness ✓ Testability ✓ Usability ✓ Maintainability ✓ Modifiability ✓
174. Command Query Responsibility Segregation
175. CQRS
176. Slide: Microsoft
181. https://gnugat.github.io/ 2016/05/11/towards-cqrs- command-bus.html
185. Controller Domain Framework
186. Event Sourcing
187. Event Sourcing •Store the Events That Happen •Append Only Event Storage •Object Properties are Not Stored
191. Event Sourcing •Avoids Data Mapping •Avoids Object-relational Impedance Mismatch •Reduces Database Table Counts (Related Tables) •Potentially Reduces Model Counts
192. Slide: Microsoft
196. Libraries •https://github.com/szjani/predaddy •https://github.com/prooph •https://github.com/qandidate-labs/broadway
197. Learning More
199. DevBookClub https://www.youtube.com/user/devbookclub
205. DDDinPHP Google Group http://DDDinPHP.org
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