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Taking a Gamble with Functional Domain Modeling
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Presentation for Functional Domain Modeling where I cover how to identify/implement the domain for Blackjack. From there, we take a look at implementing various workflows by exploring the Maybe type!
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Taking a Gamble with Functional Domain Modeling
- 1. @pcameronpresley Taking a Gamble With Functional Domain Modeling Cameron Presley Cameron@TheSoftwareMentor.com
- 4. @pcameronpresley What Are We Covering? Introduction to Blackjack Defining the Domain Implementing the Domain Implementing common workflows 4
- 5. 5
- 6. @pcameronpresley Overview Game played with a standard deck of cards Objective is to get closest to 21 points without going over Involves one or more players playing against the dealer 6
- 7. @pcameronpresley Set Up Each player is dealt two cards face-up to form their hand Dealer is dealt two cards (one face-up) to form their hand 7
- 8. @pcameronpresley Game Play On their turn, a player can take an action Once all players have taken their turn, dealer takes their turn After dealer completes their turn, each player compares their hand with the dealer 8
- 9. @pcameronpresley Player Turn Players can either “Hit” or “Stand” ◦ Stand – Ends the turn, staying in ◦ Hit – Draw a card If their hand goes over 21, they “bust” ending their turn and leaving the round 9
- 10. @pcameronpresley Scoring Aces can be worth 1 or 11 points Face cards are worth 10 points Number cards are worth that many points If a player or dealer is dealt a hand worth 21 points (an Ace and a 10 point card), they have a Blackjack, winning automatically 10
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- 13. @pcameronpresley What are the nouns? Game played with a standard deck of cards Objective is to get closest to 21 points without going over Involves one or more players playing against the dealer 13
- 15. @pcameronpresley Each player is dealt two cards face-up to form their hand Dealer is dealt two cards (one face-up) to form their hand 15
- 17. @pcameronpresley On their turn, a player can take an action Once all players have taken their turn, dealer takes their turn After dealer completes their turn, each player compares their hand with the dealer 17
- 19. @pcameronpresley Players can either “Hit” or “Stand” ◦ Stand – Ends the turn, staying in ◦ Hit – Draw a card If their hand goes over 21, they “bust” ending their turn and leaving the round 19
- 21. @pcameronpresley Building Up the Dependency Chart 21
- 22. @pcameronpresley Determining Dependencies using “has-a” Game has a Deck, a Dealer, and Players Deck has one or more Cards Dealer has a Hand Player has a Hand Hand has one or more Cards Card has a Rank and Suit 22
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- 28. @pcameronpresley Rank Represents one of 13 possible values Rank can be an Ace OR a Two OR a Three… How to Model? 28
- 29. @pcameronpresley Introducing The Sum Type! Type that can be one of a finite number of choices Each choice is a different constructor When a type can be A or B or C 29
- 32. @pcameronpresley Suit Represents one of four possible values Suit can be Hearts or Clubs or Spades or Diamonds How can we model this? 32
- 35. @pcameronpresley Card Represents the combination of any Rank and Suit 13 Ranks x 4 Suits = 52 possibilities How can we model combinations? 35
- 36. @pcameronpresley Introducing the Product Type! Type that specifies the combination of other types It’s the product of the possible values for all types it combines 36
- 39. @pcameronpresley Deck Represents the Cards to be used in the game Players and Dealers will be drawing from this during the Game How to model? 39
- 40. @pcameronpresley Introducing the Type Alias! 40 Any code that can work on a Card List will work on a Deck
- 42. @pcameronpresley Hand Represents one or more Cards that a Player or Dealer has How to model this? Leveraging a Type alias! 42
- 43. @pcameronpresley 43 Any issue with Hand and Deck being interchangeable?
- 44. @pcameronpresley Making Deck Different 44 In order to create this type, a Card list must be specified Deck != Card list
- 47. @pcameronpresley Player Represents someone playing the game Has a Hand and an ID How to model? 47
- 50. @pcameronpresley Dealer Represents who every player is competing against Has a Hand How to model? 50
- 53. @pcameronpresley Game It’s what’s being played! Consists of a Deck, a Dealer, and 1 or more Players How to Model? 53
- 56. @pcameronpresley Status Represents the Player or Dealer during the game Can be one of 3 possible values - Blackjack, Busted, Stayed How to model? 56
- 57. @pcameronpresley Status 57 To construct Stayed or Busted, an integer is needed No dependencies to construct the Blackjack type
- 59. @pcameronpresley Points Represents how much a Card is worth Ace = 1 or 11 points Face Cards = 10 points Number Cards = That number of points How to model? 59
- 60. @pcameronpresley Points 60 To construct the Hard type, need an int To construct the Soft type, need a tuple of int and int
- 62. @pcameronpresley Action Represents what a Player can do during the Game Can either be Hit or Stay How to model? 62
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- 70. @pcameronpresley Scoring a Hand How Would You Score a Hand? Calculate how many points each card is worth Sum them up! 70
- 71. @pcameronpresley Scoring Rules Aces can be worth 1 or 11 points Face cards are worth 10 points Number cards are worth that many points 71
- 73. @pcameronpresley How to add points? 73
- 75. 75
- 76. @pcameronpresley Drawing A Card! 76 What do we do if the deck is empty?
- 77. @pcameronpresley Introducing the Maybe Type! Allows us to model the absence of a value Compile time checked Forces us to do the right thing 77
- 78. @pcameronpresley 78 Most languages have this construct In F#, it’s called Option
- 79. @pcameronpresley 79 By using Option, we’re signaling that this function may return a value and that callers will need to deal with the absence of value
- 80. @pcameronpresley Let’s Draw Multiple Cards! 80
- 82. @pcameronpresley 82 Where did maybe come from? Where did let! come from? Where did return come from?
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- 85. @pcameronpresley What Did We Cover? Introduction to Blackjack Defining the Domain Implementing the Domain Implementing common workflows 85
- 87. @pcameronpresley Resources ◦ Thinking Functionally (series) by Scott Wlaschin ◦ Functional Architecture : a definition by Mark Seemann ◦ Functional Architecture Is Ports and Adapters by Mark Seemann ◦ Algebraic Data Types Aren't Numbers on Steroids by Mark Seemann ◦ Domain Modeling Made Functional by Scott Wlaschin