php[world] 2017 Domain-Driven Design Workshop

Transcript

1. Domain-Driven
   Design
   Deconstructed
   Domain-Driven
   Design
   Deconstructed
   Andrew Cassell
   @alc277 andrewcassell.com
   

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8. Domain-Driven
   Design
   

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9. Domain-Driven
   Design
   

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11. Common Sense
    Software
    Development
    

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22. Encapsulation &
    Immutability &
    Modeling &
    Behavior
    

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23. Domain
    

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24. Domain
    

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25. BEER
    

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30. Photo: Kathleen Pierce - Bangor Daily News
    

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42. Brewing
    Software
    

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54. recipe
    hop
    grain
    hop_inventory
    grain_inventory
    recipe_hop_link
    user
    recipe_user_link
    brew_event
    ROLE_USER
    ROLE_ADMIN
    

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55. Source: http://jonclaytonbiz.com/
    

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

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62. #JBTD
    (http://jobstobedone.org/)
    

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64. YYYYY
    

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65. Why?
    Why?
    Why?
    Why?
    Why?
    

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66. Search
    Caluclation
    List
    Automation
    

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67. DDD !=
    

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73. http://www.csharpstar.com/
    

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75. DDD CRUD
    Correctness
    Testability
    Usability
    Maintainability
    Modifiability
    

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

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78. DDD CRUD/MUD
    Recipe Building Inventory
    Brewhouse Activity Beer Menu / Prices
    Brew Sessions Brewery Website
    Calclations QA Record Keeping
    

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79. Who is
    responsible
    

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84. Ubiquitous
    Language
    

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85. Ubiquitous Language
    Developers
    Domain
    Experts
    

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86. Ubiquitous
    Language
    

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87. User
    Brewer
    Employee
    Taster
    Customer
    

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

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90. $recipe = BeerRecipe::findOrFail($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();
    

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92. Ubiquitous Language
    $recipe->addGrains($grains);
    Code:
    We need to be able to add a measured amount
    of grain to a recipe.
    Business:
    

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93. Ubiquitous Language
    $recipe->getEstimatedAlcoholByVolumeABV();
    Code:
    We need to be able to calculate an estimated
    ABV for a recipe.
    Business:
    

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94. Ubiquitous Language
    $storage = (new StorageFacilities())->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.
    

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95. 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 = HopQuantity::(“Simcoe”,”12%AA”,”.2oz per gallon”);
    Business:
    

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96. @recipe
    Feature: A user should be able to dry hop a recipe
    Scenario: User adds dry hops to recipe
    Given I am authenticated as a user
    And I am on “/recipe/0ef360fd“
    And I press "Add Hops”
    And I fill out form with:
    | Hop Name |
    | Simcoe |
    Then I see “Alpha Acid: 11.5 - 15.0“
    

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97. $recipe->dryHop($hop);
    $recipe->addIngredient($hop);
    $recipe->addToBoil($hop);
    $recipe->addToBoilKettle($hop);
    $recipe->addToBoiler($hop);
    $recipe->addFirstWortHop($hop);
    $recipe->addToFermenter($hop);
    $recipe->addToMashTun($hop); //fails
    

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98. $hop = (new HopsSupply(…))->findOneByName(‘Simcoe’);
    $catalog = new RecipeCatalog(…);
    $recipe = $catalog->findOneRecipeByName(‘iPHPA’);
    $recipe->addDryHop($hop, new DryHopSchedule(‘7 Days’));
    $brewers = new Brewers(…);
    $brewer = $brewers->findOneByUsername(‘cassell’);
    $brewSession = $brewer->brew($recipe);
    $brewSession->dryHopsWereAdded($hop, Datetime::now());
    

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99. $hop = (new HopsSupplyRepo())->findOneByName(‘Simcoe’);
    $catalog = new RecipeCatalogRepository(…);
    $recipe = $catalog->findOneRecipeByName(‘iPHPA’);
    $recipe->addDryHop($hop, new DryHopSchedule(‘7 Days’));
    $brewers = new BrewersRepository(…);
    $brewer = $brewers->findOneByUsername(‘cassell’);
    $brewSession = $brewer->brew($recipe);
    $brewSession->dryHopsWereAdded($hop, Datetime::now());
    

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100. CRUD/MUD DDD
     Users Brewers
     String RecipeName
     Integer IBU
     Float(7,3) AlphaAcid
     Array of ORM Objects GrainBill
     BeerInventoryRepositoryInterface Menu
     

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104. $hop = (new HopsSupply())->findOneByName(‘Centennial Pellets’);
     $catalog = new RecipeCatalog(…);
     $recipe = $catalog->findOneRecipeByName(‘iPHPA’);
     $recipe->addDryHop($hop, new DryHopSchedule(‘7 Days’));
     $brewers = new Brewers(…);
     $brewer = $brewers->findOneByUsername(‘cassell’);
     $brewSession = $brewer->brew($recipe);
     $brewSession->dryHopsWereAdded($hop, Datetime::now());
     

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105. […], 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.
     

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

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108. The Brewer, designed and engraved in the Sixteenth Century, by Jost Amman.
     

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109. Inventory
     Marketing
     Finance
     Production
     “Hop”
     

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110. Quantity at a Location
     Flavor
     Expenditure
     Ingredient
     “Hop”
     

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111. Bounded
     Contexts
     

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112. Inventory
     Recipes Brewhouse
     

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113. Slide: Vaughn Vernon
     

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115. Inventory
     Recipes Brewhouse
     

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116. Inventory
     Recipes Brewhouse
     

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117. Message
     Inventory
     Recipes Brewhouse
     

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118. Domain Event
     Inventory
     Recipes Brewhouse
     

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124. Personas
     

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125. adaptivepath.com
     

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126. 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.
     

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131. https://blog.intercom.io/using-job-stories-design-features-ui-ux/
     

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134. 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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135. User Research
     

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136. Photo: Mathias Verraes
     

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137. Command
     Actor
     Model
     Domain
     Event
     

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138. Domain Event
     • Something that happens in the
     software.
     • Past Tense
     

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139. Domain Event
     • Beer Was Brewed
     • Grain Was Added
     • Hops Were Added
     • Brewer Changed Email Address
     

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149. Command
     Actor
     Model
     Domain
     Event
     

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150. Command
     • The action that precipitates the event
     • Written in Present Tense
     

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151. Command
     • Start Brewing Session
     • Add Grain to Recipe
     • Add Hops To Fermenter
     • Change Email Address
     

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154. Command
     Actor
     Model
     Domain
     Event
     

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155. Model
     • Command is acted upon this thing
     • Might Include Supporting Models
     

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156. Model
     • Recipe
     • Ingredient
     • Brewer
     

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158. Command
     Actor
     Model
     Domain
     Event
     

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159. Actor
     • Who did it?
     • If you only have one user you might
     not need this
     

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162. Command
     Actor
     Model
     Domain
     Event
     

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165. business
     origami
     

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166. Jess McMullin
     Business Origami
     

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167. Jess McMullin
     Business Origami
     

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168. Jess McMullin
     Business Origami
     

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169. Sean Jalleh
     

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172. Source: Jeff Patton
     

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

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179. Domain Objects
     Value Objects
     Domain Events
     Entities
     Aggregates
     

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180. Value Object
     Immutable
     No Identity (Only Values)
     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
     

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181. Value Objects
     

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182. Email Address
     Recipe Name
     Date We Brewed On
     Weight
     Temperature
     Value Objects
     

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183. Value Objects
     Email Address
     Recipe Name
     Date We Brewed On
     Weight
     Temperature
     Ubiquitous
     Language
     

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184. Value Objects
     EmailAddress
     RecipeName
     BrewedOn
     Pounds
     DegreesFahrenheit
     Email Address
     Recipe Name
     Date We Brewed On
     Weight
     Temperature
     

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

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186. Immutable
     

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187. Immutable
     Avoid Spooky
     Action at a
     Distance
     

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188. ALWAYS
     VALID
     Value Objects
     

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189. Value Objects
     

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

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

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192. Plain PHP Objects
     (POPOs)
     Value Objects
     

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193. Plain 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
     

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194. Only depend on
     scalars or other value
     objects.
     Value Objects
     

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195. They are not
     dependencies that
     you inject.
     Value Objects
     

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196. RecipeName
     Example
     

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201. 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.
     

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203. 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.
     .EE 3 / 3 (100%)
     Time: 1.56 seconds, Memory: 4.00MB
     There were 2 errors:
     1) Beeriously\Tests\Unit\Domain\Recipe\RecipeNameTest::testGetter
     Error: Call to undefined method Beeriously\Domain\Recipe\RecipeName::getValue()
     /app/src/Tests/Unit/Domain/Recipe/RecipeNameTest.php:21
     2) Beeriously\Tests\Unit\Domain\Recipe\RecipeNameTest::testToString
     Object of class Beeriously\Domain\Recipe\RecipeName could not be converted to string
     /app/src/Tests/Unit/Domain/Recipe/RecipeNameTest.php:27
     ERRORS!
     Tests: 3, Assertions: 2, Errors: 2.
     cassell:beeriously cassell$
     

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205. 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.
     ..E 2 / 3 (67%)
     Time: 292 ms, Memory: 4.00MB
     There was 1 error:
     1) Beeriously\Tests\Unit\Domain\Recipe\RecipeNameTest::testToString
     Object of class Beeriously\Domain\Recipe\RecipeName could not be converted to string
     /app/src/Tests/Unit/Domain/Recipe/RecipeNameTest.php:27
     ERRORS!
     Tests: 35, Assertions: 78, Errors: 1.
     make: *** [unit] Error 2
     cassell:beeriously cassell$
     

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207. 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)
     

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210. BrewedOn
     Example
     

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214. Pounds
     Example
     

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218. $poundA->reduceBy($poundB);
     

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219. Eliminates Checking
     Value Objects
     

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221. Factories
     $weight = $factory->create(‘2 lbs’);
     

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222. Static
     Constructors
     

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223. Natural
     Language
     Constructors
     

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226. Temperature
     Example
     

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232. Composite
     Value Objects
     

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233. Full Name
     First Name + Last Name
     

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235. Encoding
     Business Logic in
     Value Objects
     

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236. Amount of
     Alcohol
     

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238. ABV
     

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239. Sugar + Yeast =
     Alcohol + CO2
     

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240. Sugar + Yeast =
     Alcohol + CO
     2
     C H O ->2C H OH + 2CO
     6 12 6 2 5 2
     

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241. Sugar + Yeast =
     Alcohol + CO2
     

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242. Sugar + Yeast =
     Alcohol + CO2
     

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243. Sugar - Sugar = Alcohol
     START FINISH
     

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244. Sugar - Sugar = Alcohol
     START FINISH
     Volume
     Volume
     

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245. Specific Gravity
     

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247. Hydrometer
     

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249. learntomoonshine.com
     

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250. Michael L. Hall - Zymurgy, Summer 1995, vol. 18, no. 2
     

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270. DDD CRUD/MUD
     RecipeName String
     Temperature Float(7,3)
     DateBrewed DateTime
     Gravity Float(7,3)
     ABV Function + Validation?
     

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

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273. Entities
     

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274. Identifiable
     Have State and are Mutable (Lifecycle)
     Never in an Invalid State
     Operate using Value Objects
     No Security or Permission Checks
     *(Ideally) Storage Agnostic
     Entities
     

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275. DO AS MUCH AS
     YOU CAN IN
     VALUE OBJECTS!
     

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276. Doctrine Mappings
     Doctrine Annotations
     Laravel Eloquent ORM
     “Storage Agnostic”
     

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277. BEHAVIOR FIRST!
     STORAGE SECOND!
     “Storage Agnostic”
     

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278. Single Entity
     Entities
     Regular Aggregate
     Contain Other
     Entities
     

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279. Brewer
     Grain
     Hops
     BeerOnTap
     Entity Types
     Regular Aggregate
     Invoice
     Recipe
     BrewSession
     BeerMenu
     

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280. 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, …
     

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282. SETTERS
     ARE BAD
     

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287. Calling two setters in a row
     on the same object
     Missing a Concept?
     

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288. Calling two methods in a row
     on the same object
     Missing a Concept?
     

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289. Passing more than one
     parameter to a method
     Missing a Concept?
     

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292. Doctrine
     

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302. Bounded
     Contexts
     

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303. Inventory
     Recipes Brewhouse
     

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304. Inventory
     Recipes
     Brewhouse
     Recipe\Grain
     Inventory\Grain
     Brewing\BrewSession\Grain
     

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305. Inventory
     Recipes Brewhouse
     

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306. Inventory
     Recipes Brewhouse
     Brewers
     Supporting Bounded Context
     

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307. • Entities
     • Manages Child Entities
     • Transactional Boundary
     • The Easiest Models to Identify
     Aggregates
     

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308. Aggregates
     Recipe
     BrewSession
     BeerMenu
     

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

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319. Task Based
     User Interface
     

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320. View Slide

321. View Slide

322. View Slide

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

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324. View Slide

325. Security
     

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

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327. Controller
     Domain
     Framework
     

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328. View Slide

329. View Slide

330. View Slide

331. View Slide

332. Controller
     Domain
     Framework
     

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

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

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335. View Slide

336. View Slide

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

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

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339. Domain
     Events
     

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340. 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
     

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341. View Slide

342. BrewSessionWasPlanned
     

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343. BrewSessionWasPlanned
     

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344. View Slide

345. View Slide

346. View Slide

347. View Slide

348. View Slide

349. View Slide

350. View Slide

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

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352. Business
     Rules in a
     Specification
     

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353. View Slide

354. View Slide

355. View Slide

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

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357. View Slide

358. Command Query
     Responsibility
     Segregation
     

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359. CQRS
     

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360. Write Read
     

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361. Write
     Model
     Read
     Model(s)
     

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362. Write
     Domain
     Model
     Read
     Model(s)
     

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363. Controller
     Command Bus
     Handler Handler Handler
     

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364. Controller
     Command Bus
     Handler Handler Handler
     Request
     

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365. Controller
     Command Bus
     Handler Handler Handler
     Command
     

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366. View Slide

367. View Slide

368. Controller
     Command Bus
     Handler Handler Handler
     Command
     

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369. Controller
     Command Bus
     Handler Handler Handler
     Command
     

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370. Controller
     Command Bus
     Handler Handler Handler
     Command
     

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371. Controller
     Command Bus
     Handler Handler Handler
     Response
     

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372. Controller
     Command Bus
     Handler Handler Handler
     Response
     

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373. Controller
     Command Bus
     Handler Handler Handler
     Response
     

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

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375. View Slide

376. View Slide

377. View Slide

378. View Slide

379. View Slide

380. View Slide

381. Why Do CQRS?
     

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382. Controller
     Domain
     Framework
     

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383. Controller
     API (versions?)
     Console Commands
     

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384. Event
     Sourcing
     

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385. View Slide

386. View Slide

387. View Slide

388. Event Sourcing
     • Object Properties are Not Persisted
     • Events Are Persisted to 

     Append Only Event Storage
     

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

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390. Slide: Microsoft
     

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391. Libraries
     • https://github.com/broadway
     • https://github.com/prooph
     • https://github.com/szjani/predaddy
     

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392. Recipe
     Example
     

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393. Learning
     More
     

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394. homebrewersassociation.org
     

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395. View Slide

396. View Slide

397. DEV BOOK CLUB
     https://www.youtube.com/user/devbookclub
     

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398. View Slide

399. View Slide

400. View Slide

401. View Slide

402. View Slide

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

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404. Final Thoughts
     

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405. View Slide

406. View Slide

407. View Slide

408. View Slide

409. View Slide

410. View Slide

411. Inventory
     Recipes Brewhouse
     

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412. Inventory
     Recipes Brewhouse
     Legacy
     Context
     

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413. View Slide

414. View Slide

415. https://joind.in/talk/ee152
     DDD Topics Covered
     •Ubiquitous Language
     •Event Storming
     •Modelling
     •Value Objects
     •Entities
     •Aggregates
     •Hexagonal Architecture
     •CQRS
     •Event Sourcing
     

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