Domain-driven Design Workshop

FWDAYS May 21, 2020

Workshop: Building PHP applications using domain-driven design (DDD) techniques
The workshop is available only for participants of the PHP fwdays’20 conference who purchased a ticket till April 10. The form with registration for the workshop was sent to the email.

The workshop will be held in an online format in Zoom app. Please, install it on your device to follow the workshop. The number of participants is 30.

Workshop from Andrew Cassell is aimed at developers with Knowledge of PHP and object oriented programming. Audience and level: Intermediate and up. The workshop will be held in English.

Building PHP applications using domain-driven design (DDD) techniques results in code that is easier to modify, maintain, test, and makes for a better user experience. In this hands-on tutorial, you will become versed in the best practices for solving problems using domain-driven design in PHP from start to finish. You will learn to:

Discover a ubiquitous language and identify changes in the design of PHP classes, methods, and problem-solving
Use Event Storming build the best software for the client/user
Assemble an incorruptible domain model in PHP
Use bounded contexts and domain events to better organize code and make it more modular
Employ best practices for persisting and accessing entities and aggregate roots in Doctrine, Eloquent, Zend, etc
Use advanced PHP object-oriented techniques to simplify code and reduce state complexity
Plan for change by using the Hexagonal Architecture Pattern
Evaluate when and how to use CQRS and Event Sourcing techniques
Introduce DDD to a “legacy” codebase
Discover recommended resources for learning more about applying DDD in PHP

Transcript

1. D ain-D iven Design Workshop D ain-D iven Design Workshop Andrew Cassell @alc277 andrewcassell.com
2. available on
3. 1 About CURIOSITYSTREAM • Founded by John Hendricks, founder of the Discovery Channel • Thousands of documentaries and series • HD and 4K • Available worldwide
4. 4 WE ARE HIRING! https://jobs.daxx.com/browse-jobs/?search_keywords=curiositystream
8. github.com/cassell
9. BEER
10. Good Code?
11. Testable SOLID Less Defensive
14. Monolith Microservices Serverless
19. Domain-Driven Design
20. Domain-Driven Design
21. Common Sense Software Development
29. $car->bark(); $dog->drive();
31. Encapsulation Modeling Behavior
32. Domain
33. available on
34. BEER
36. Photo: Kathleen Pierce - Bangor Daily News
43. Brewing Software
48. recipe hop grain hop_inventory grain_inventory recipe_hop_link user recipe_user_link brew_event ROLE_USER ROLE_ADMIN
49. Source: http://jonclaytonbiz.com/
52. People don't want to buy a quarter-inch drill, they want a quarter- inch hole. Theodore Levitt
56. #JBTD (http://jobstobedone.org/)
58. YYYYY why? why? why? why? why?
59. Why? Why? Why? Why? Why?
60. Search Caluclation List Automation
61. DDD !=
67. http://www.csharpstar.com/
69. DDD CRUD Correctness Testability Usability Maintainability Modifiability
71. DDD BALL OF MUD / CRUD Correctness Testability Usability Maintainability Modifiability
72. DDD CRUD/MUD Recipe Building Inventory Brewhouse Activity Beer Menu / Prices Brew Sessions Brewery Website Calclations QA Record Keeping
73. Who is responsible
78. Ubiquitous Language
79. Ubiquitous Language Developers Domain Experts
81. Ubiquitous Language
82. User Brewer Employee Taster Customer
84. 1. Naming Things 2. Cache Invalidation 3. Off By One Errors Top 10 Reasons Programming is Hard
85. $recipe = BeerRecipe::findOrFail($uuid); $hop = HopRepo::where(“name”,”=“,”Simcoe”)->take(1)->get(); if (!$recipe->hopsArray()->contains(‘hop_id’,$hop->id)) { $recipe->hopsArray()->attach($hop->id, [‘weight' => 1.0]); } $recipe->save();
87. Ubiquitous Language $recipe->addGrains($grains); Code: We need to be able to add a measured amount of grains to a recipe. Business:
88. Ubiquitous Language $recipe->getEstimatedAlcoholByVolumeABV(); Code: We need to be able to calculate an estimated ABV for a recipe. Business:
89. Ubiquitous Language $facilities = new StorageFacilities(); // from container $storage = $facilities->findByOneName(“Silo #4”); $storage->howMuchOfGrainType(new GrainType(‘Winter Wheat’)); Business: Code: We need to know how much Winter Wheat is in our storage silo #4.
90. Ubiquitous Language $recipe->addDryHop($hopQuantity, $schedule); Code: We need to add .2oz of 12% AA per gallon of Simcoe hops to a recipe 7 days after the boil is complete. This is called dry hopping. $schedule = new DryHopSchedule(‘7 Days’); $hopQuantity = new HopQuantity(“Simcoe”,”12%AA”,”.2oz per gallon”); Business:
91. $recipe->dryHop($hop); $recipe->addIngredient($hop); $recipe->addToBoil($hop); $recipe->addToBoilKettle($hop); $recipe->addToBoiler($hop); $recipe->addFirstWortHop($hop); $recipe->addToFermenter($hop);
92. $hop = (new HopsSupplier(…))->findOneByName(‘Simcoe’); $catalog = new RecipeCatalog(…); $recipe = $catalog->findOneRecipeByName(‘iPHPA’); $recipe->addDryHop($hop, new DryHopSchedule(‘7 Days’)); $brewers = new Brewers(…); $brewer = $brewers->findOneByUsername(‘cassell’); $brewSession = new BrewSession($brewer, $recipe, new Datetime()); $brewSession->dryHopsWereAdded($hop, new Datetime());
93. $hop = (new HopsSupplierRepository(…))->findOneByName(‘Simcoe’); $catalog = new RecipeCatalogRepository(…); $recipe = $catalog->findOneRecipeByName(‘iPHPA’); $recipe->addDryHop($hop, new DryHopSchedule(‘7 Days’)); $brewers = new BrewersRepository(…); $brewer = $brewers->findOneByUsername(‘cassell’); $brewSession = new BrewSession($brewer, $recipe, new Datetime()); $brewSession->dryHopsWereAdded($hop, new Datetime());
94. CRUD/MUD DDD Users Brewers String RecipeName Integer IBU Float(7,3) AlphaAcid Array of ORM Objects GrainBill BeerInventoryRepositoryInterface Menu
95. […], we want to establish the idea that a computer language is not just a way of getting a computer to perform operations but rather that it is a novel formal medium for expressing ideas about methodology. Thus, programs must be written for people to read, and only incidentally for machines to execute.
96. DDD BALL OF MUD/CRUD Correctness ✓ Testability Usability Maintainability Modifiability
98. The Brewer, designed and engraved in the Sixteenth Century, by Jost Amman.
99. Inventory Marketing Finance Production “Hop”
100. Quantity at a Location Flavor Expenditure Ingredient “Hop”
101. Bounded Contexts
102. Inventory Recipes Brewhouse
103. Slide: Vaughn Vernon
105. Inventory Recipes Brewhouse
106. Inventory Recipes Brewhouse
107. Message Inventory Recipes Brewhouse
108. Domain Event Inventory Recipes Brewhouse
114. Personas
115. adaptivepath.com
116. Photos: Terry Brown and Gordon Stettinius Alice Shane P.J. Sam George Male Age 32 Brewer for 3 Years Got into brewing after the record store he worked at closed. Is very tech savvy and carries an Android. Male Age 50 Brewing for 10 Years Just Promoted to COO Retired civil servant who believes software can make a brewery for regulatory compliant. Female Age 27 New Hire Library science graduate who was just hired away from the local university. iPhone user. Male Age 52 Librarian for 30 years Has been brewing beer as long as he can remember. Loves beer podcasts but is not a fan of technology. Male Age 46 Brewer for 20 Years Loves poetry and writing. Brewing is just a job to pay the bills.
121. https://blog.intercom.io/using-job-stories-design-features-ui-ux/
124. 7 Dirty Words When Meeting With a Domain Expert 1.Session 2.Repository 3.Abstract 4.Interface 5.Class 6.Database 7.Foreign Key
125. User Research
126. Photo: Mathias Verraes
128. Command Actor Model Domain Event View Whatever
129. Domain Event • Something that happens in the software. • Past Tense
130. Domain Event • Beer Was Brewed • Grain Was Added • Hops Were Added • Brewer Changed Email Address
141. https://bit.ly/2LL1Xib
142. Command Actor Model Domain Event
143. Command • The action that precipitates the event • Written in Present Tense
144. Command • Start Brewing Session • Add Grain to Recipe • Add Hops To Fermenter • Change Email Address
148. Command Actor Model Domain Event
149. Model • Command is acted upon this thing • Might Include Supporting Models
150. Model • Recipe • Ingredient • Brewer
151. Command Actor Model Domain Event
152. Actor • Who did it? • If you only have one user you might not need this
155. Water profiles change daily
156. Command Actor Model Domain Event
160. Source: Jeff Patton
162. business origami
163. Jess McMullin Business Origami
164. Jess McMullin Business Origami
165. Sean Jalleh
167. DDD BALL OF MUD/CRUD Correctness ✓✓ Testability Usability ✓ Maintainability Modifiability
168. Domain Model
169. Domain Objects Value Objects Domain Events Entities Aggregates
170. Value Object No Identity (Only Values) *Immutable Hop Name Amount Paid Temperature Entity Identifiable Mutable Lifecycle Contains Value Objects Line Item Brewer Water Chemistry Aggregate Entity Responsible For Child Entities Transaction Boundary Invoice Recipe Brew Session
171. OBJECTS FOR ALL THE THINGS
172. Value Objects
173. Email Address Recipe Name Date We Brewed On Weight Temperature Value Objects
174. Value Objects Email Address Recipe Name Date We Brewed On Weight Temperature Ubiquitous Language
175. Value Objects EmailAddress RecipeName BrewedOn Pounds DegreesFahrenheit Email Address Recipe Name Date We Brewed On Weight Temperature
176. Plain Old PHP Objects (POPOs) Value Objects
178. Not Just Static Typing https://github.com/Fiedzia/type-system-research/blob/master/README.md Value Objects
189. Passed in by Reference / Pointer
194. Spooky Action at a Distance
201. Mutable objects depend on state.
203. Mutable objects depend on time.
204. $mutable->function(a,b,c) { global $time; //… } $immutable->function(a,b,c) { //… }
205. $mutable->getValue() { global $time; return $value($time); } $immutable->getValue() { return $value; }
206. My pragmatic summary: A large fraction of the flaws in software development are due to programmers not fully understanding all the possible states their code may execute in.
207. Immutability
208. Function
209. value Mutable
210. 42 Mutated
211. value Immutable
212. value Immutable
213. value Immutable
214. value Immutable
215. Mutable Immutable Read-Only After Creation Read & Write
216. They are not dependencies that you inject. Value Objects
219. IMMUTABLE AND ALWAYS VALID Value Objects
220. Value Objects
222. “Gateway Drug to Test Driven Development” Value Objects
223. “Gateway Drug to Test Driven Development” Value Objects #MYTESTSDONTPASS
224. Plain Old PHP Objects (POPOs) • Declare Class Properties as Private • No Setters (behaviors will return new) • No References to Mutable Objects • Throw Exceptions in Constructor Value Objects
225. Only depend on scalars or other value objects. Value Objects
226. RecipeName Example
230. cassell:beeriously cassell$ docker run --rm --interactive --tty --network beeriously_default --volume `pwd`:/app --user : --workdir /app beeriously_php-fpm /app/vendor/bin/phpunit --configuration /app/src/Tests/Unit/ phpunit.xml.dist PHPUnit 6.4.3 by Sebastian Bergmann and contributors. FEE 3 / 3 (100%) Time: 2.34 seconds, Memory: 4.00MB There were 2 errors: 1) Beeriously\Tests\Unit\Domain\Recipe\RecipeNameTest::testGetter Error: Class 'Beeriously\Domain\Recipe\RecipeName' not found /app/src/Tests/Unit/Domain/Recipe/RecipeNameTest.php:20 2) Beeriously\Tests\Unit\Domain\Recipe\RecipeNameTest::testToString Error: Class 'Beeriously\Domain\Recipe\RecipeName' not found /app/src/Tests/Unit/Domain/Recipe/RecipeNameTest.php:26 -- There was 1 failure: 1) Beeriously\Tests\Unit\Domain\Recipe\RecipeNameTest::testEmptyFails Failed asserting that exception of type "Error" matches expected exception "Beeriously\Domain\Recipe\InvalidRecipeNameException". Message was: "Class 'Beeriously\Domain\Recipe\RecipeName' not found" at /app/src/Tests/Unit/Domain/Recipe/RecipeNameTest.php:15 . ERRORS! Tests: 3, Assertions: 1, Errors: 2, Failures: 1.
233. cassell:beeriously cassell$ docker run --rm --interactive --tty --network beeriously_default --volume `pwd`:/app --user : --workdir /app beeriously_php-fpm /app/vendor/bin/phpunit --configuration /app/src/Tests/ Unit/phpunit.xml.dist PHPUnit 6.4.3 by Sebastian Bergmann and contributors. ... 3 / 3 (100%) Time: 192 ms, Memory: 4.00MB OK (3 tests, 4 assertions)
236. BrewedOn Example
240. Pounds Example
242. <?php var_dump(-0.0 > 0); // false var_dump(-0.0 < 0); // false var_dump(-0.0 === 0.0); // true (float) var_dump(-0.0 === 0); // false (int) var_dump(-0.0 == false); // true (bool) var_dump(-0.0 == null); // true (bool) var_dump(-0.0 == “”); // true var_dump(-0.0 == "negativezero"); // true (string)
244. $poundA->reduceBy($poundB);
245. Eliminate Checking Value Objects
250. What should be and Immutable Value Object?
251. Event
252. Event History
253. Request
254. Response
255. Almost Everything
256. Natural Language Constructors
257. Natural Language Factory Methods
258. Static Constructors
261. Resist the Urge to Extend
262. class Pounds extends FloatValue { //… }
263. class EmailAddress extends StringObject { //… }
266. Temperature Example
272. Composite Value Objects
273. Composite Value Objects
281. Encoding Business Logic in Value Objects
282. Alcohol by Volume
284. Sugar + Yeast = Alcohol + CO 2 C H O ->2C H OH + 2CO 6 12 6 2 5 2
285. Sugar + Yeast = Alcohol + CO2
286. Sugar - Sugar = Alcohol START FINISH
287. Sugar - Sugar = Alcohol START FINISH Volume Volume
288. Hydrometer
289. learntomoonshine.com
290. Michael L. Hall - Zymurgy, Summer 1995, vol. 18, no. 2
292. Calibration Temperature Minimum Gravity Reading Maximum Gravity Reading
316. Как тебе такое, Илон Маск?
320. DDD CRUD/MUD RecipeName String Temperature Float(7,3) DateBrewed DateTime Gravity Float(7,3) ABV Function + Validation?
321. DDD BALL OF MUD/CRUD Correctness ✓✓ Testability ✓ Usability ✓ Maintainability Modifiability
322. Domain Entities
324. Entities Identifiable Have State and are Mutable (Lifecycle) Operate using Value Objects *(Ideally) Storage Agnostic *(Ideally) Never in an Invalid State
325. DO AS MUCH AS YOU CAN IN VALUE OBJECTS!
326. Doctrine Zend Hydrator *Laravel Eloquent ORM “Storage Agnostic”
327. BEHAVIOR FIRST! STORAGE SECOND! “Storage Agnostic”
328. Single Entity Entities Regular Aggregate Contain Other Entities
329. Brewer Grain Hops BeerOnTap Entity Types Regular Aggregate Invoice Recipe BrewSession BeerMenu
330. Making an Entity: Brewer Identifiable ID (UUID) Mutable $brewer->changeUsername() $brewer->changeName() $brewer->changeEmail() Never in an Invalid State __construct Operate Using Value Objects FullName, EmailAddress, …
333. SETTERS ARE BAD
338. Calling two setters in a row on the same object Missing a Concept?
339. Calling two methods in a row on the same object Missing a Concept?
340. Passing more than one parameter to a method Missing a Concept?
343. Doctrine
360. Bounded Contexts
361. Inventory Recipes Brewhouse
362. Inventory Recipes Brewhouse Recipe\Grain Inventory\Grain Brewing\BrewSession\Grain
363. Inventory Recipes Brewhouse
364. Inventory Recipes Brewhouse Brewers Supporting Bounded Context
365. Mathias Verraes - Mathias Verraes - Emergent Boundaries https://www.youtube.com/watch?v=ECM1rPYxvD4
366. • Entities • Manages Child Entities • Transactional Boundary • The Easiest Models to Identify Aggregates
367. Aggregates Recipe BrewSession BeerMenu
374. Immutable “Entity”
381. Immutable Book Mutable Price
382. $book->setPrice(16.96); $price = new Price($book,15.00) $price->setAmount(16.96); Mutable Immutable
383. $book->setPrice(16.96); $amount = new Amount(16.96, new Currency(‘USD’); $price = new BookPrice($book, $amount); $price->change(new Amount(15.99, new Currency(‘USD’)); Mutable Immutable
384. Immutable Collections
385. npm install immutable
386. <script src="immutable.min.js"></ script> <script> var map1 = Immutable.Map({ a: 1, b: 2, c: 3 }); var map2 = map1.set('b', 50); map1.get('b'); // 2 map2.get('b'); // 50 </script>
389. Value Object
391. “Immutable” Collection of Entities
399. $recipe->addGrain() $recipe->removeGrain() $recipe->updateGrain()
400. $object->create(x) $object->read(x) $object->update(x) $object->delete(x)
401. $object->create(x) { // validate x }
402. $object->read(x) { // validate x }
403. $object->update(x) { // validate x }
404. $object->delete(x) { // validate x }
409. Validate Once Not Validating Transitions Easier to Define the Rules Fewer Moving Parts
412. Entity’s job is to manage state.
413. DDD BALL OF MUD/CRUD Correctness ✓✓ Testability ✓✓ Usability ✓ Maintainability ✓✓ Modifiability ✓
414. Task Based User Interface
418. DDD BALL OF MUD/CRUD Correctness ✓✓ Testability ✓✓ Usability ✓✓ Maintainability ✓✓ Modifiability ✓
420. Security
422. Domain (Business Logic) Application Services Controller Persistence Event/Command Bus Security Templates
423. Controller Domain Module
424. Controller Domain Package
425. Controller Domain Framework
430. Controller Domain Framework
431. Mathias Verraes - Decoupling the Model from the Framework at Laracon EU 2014 https://www.youtube.com/watch?v=QaIGN_cTcc8
432. Ruby Midwest 2011 - Keynote: Architecture the Lost Years by Robert Martin https://www.youtube.com/watch?v=WpkDN78P884
434. Domain (Business Logic) Application Services Controller Persistence Event/Command Bus Security Templates
435. DDD BALL OF MUD/CRUD Correctness ✓✓ Testability ✓✓ Usability ✓✓ Maintainability ✓✓✓ Modifiability ✓
436. Domain Events
437. Domain Events • Part of the Core Domain • Happened In The Past • Important Enough To Record (Persist) • Important Enough To Concern Other Bounded Contexts • Immutable Value Objects • Do Not Contain Entities or Other Mutable Objects • Can Be Created in an Entity
439. BrewSessionWasPlanned
440. BrewSessionWasPlanned
448. Inventory Recipes Brewhouse
449. Inventory Recipes Brewhouse
450. Domain Event Inventory Recipes Brewhouse
451. Domain Event Inventory Recipes Brewhouse
452. Inventory Recipes Brewhouse Legacy Context
453. Inventory Recipes Brewhouse Legacy Context
454. Inventory Recipes Brewhouse Legacy Context
455. Inventory Recipes Brewhouse Anticorruption Layer Legacy Context Legacy Code Legacy Services
456. DDD BALL OF MUD/CRUD Correctness ✓✓✓ Testability ✓✓ Usability ✓✓ Maintainability ✓✓✓ Modifiability ✓✓
457. Specifications Repositories Factories Fetch Build/Create Filter/Evaluate Services Do Things
459. (EXCEPT CACHING!)
460. SPECIFICATION
461. Specifications $spec->isSatisfiedBy($object);
465. Example MinimumDiastaticPowerSpecification
467. CQRS
468. Command Query Responsibility Segregation (Command–query separation)
469. Write Read
470. Write Model Read Model(s)
471. Write Domain Model Read Model(s)
472. Write Domain Model Read (Complicated SQL Queries)
473. Controller Command Bus Handler Handler Handler
474. Controller Command Bus Handler Handler Handler Request
475. Controller Command Bus Handler Handler Handler Command
478. Controller Command Bus Handler Handler Handler Command
479. Controller Command Bus Handler Handler Handler Command
480. Controller Command Bus Handler Handler Handler Command
481. Controller Command Bus Handler Handler Handler Command Response
482. Controller Command Bus Handler Handler Handler Command
483. Controller Command Bus Handler Handler Handler Response
484. Controller Command Bus Handler Handler Handler Response
485. Controller Command Bus Handler Handler Handler Response
486. https://gnugat.github.io/ 2016/05/11/towards-cqrs- command-bus.html
488. Why Do CQRS?
489. Controller Domain Framework
490. Controller API (versions?) Console Commands
491. Command Bus Command Query Responsibility Segregation
492. Write Domain Model Read Model(s)
493. DDD BALL OF MUD/CRUD Correctness ✓✓✓ Testability ✓✓ Usability ✓✓ Maintainability ✓✓✓✓ Modifiability ✓✓✓
494. Event Sourcing
498. Event Sourcing • Object Properties are Not Persisted • Events Are Persisted to Append Only Event Storage
499. • Avoids Object-relational Impedance Mismatch • Reduces Database Table Counts (Related Tables) • Potentially Reduces Model Counts Event Sourcing
500. Slide: Microsoft
501. Libraries • https://github.com/eventsaucephp • https://github.com/broadway • https://github.com/prooph • https://github.com/szjani/predaddy
502. Recipe Example
503. Recipe was created with name “New Recipe” Recipe name was changed to “php[world] IPhpA” 11 pounds of 2-Row Malted Barley was added 2 pounds of Winter Wheat was added 1 pound of Vienna Malt was added 8 gallons of water was added 2 ounces of Centennial Hops for 60 Minutes 1 ounce of Centennial Hop added at whirlpool
504. Recipe Example
505. Learning More
506. homebrewersassociation.org
509. DEV BOOK CLUB https://www.youtube.com/user/devbookclub
512. https://idddworkshop.com/
515. DDDinPHP Google Group http://DDDinPHP.org
517. Final Thoughts
524. DDD Topics Covered •Ubiquitous Language •Event Storming •Modelling •Value Objects •Entities •Aggregates •Hexagonal Architecture •CQRS •Event Sourcing @alc277 andrewcassell.com