Context-Driven Development: Architecture your code with Phoenix context

Presented at 2021 ElixirConf by Jenny Shih

Note: There are quite a few gifs in the slides. They can be only uploaded as still images so some effects are gone, but that doesn't affect the values this presentation wants to convey.

Transcript

1. @jenny_codes
   Context-Driven Development
   Architect your Code with Phoenix Context
   

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4. https://media.giphy.com/media/NWtFdrEXGwZX2/giphy.gif
   

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5. • Quick onboarding
   

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6. • Quick onboarding
   
   
   • Effective
   

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7. • Quick onboarding
   
   
   • Effective
   
   
   • Using Elixir
   

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8. https://twitter.com/DJTGIF/status/856856284892729345
   Context
   

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9. What do I do with contexts?
   

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10. Outline
    • The cunning challenges of contexts
    
    
    • The quest, and what did not work
    
    
    • Build-your-own architecture
    
    
    • Revisit contexts
    
    
    • Context-driven development
    

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11. Outline
    • The cunning challenges of contexts
    
    
    • The quest, and what did not work
    
    
    • Build-your-own architecture
    
    
    • Revisit contexts
    
    
    • Context-driven development
    

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13. “Contexts are dedicated modules that
    
    
    expose and group related functionality.“
    

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14. Model
    Controller
    View
    Request Response
    

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15. Model
    Controller
    View
    /your_app_web
    /your_app
    

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16. Phoenix MVC structure
    lib
    ├── your_app
    ├── your_app_web
    Model
    Controller
    View
    /your_app_web
    /your_app
    

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17. Phoenix MVC structure
    lib
    ├── your_app
    ├── your_app_web
    ├── controllers
    ├── endpoint.ex
    ├── router.ex
    ├── templates
    └── views
    Model
    Controller
    View
    /your_app_web
    /your_app
    

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18. Phoenix MVC structure
    lib
    ├── your_app
    ├── ???
    ├── ???
    └── ???
    ├── your_app_web
    Model
    Controller
    View
    /your_app_web
    /your_app
    

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19. Phoenix MVC structure
    lib
    ├── your_app
    ├── ???
    ├── ???
    └── ???
    ├── your_app_web
    Model
    Controller
    View
    /your_app_web
    /your_app
    Context
    

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20. The cunning challenges of contexts
    

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21. The cunning challenges of contexts
    • Different layers of concerns are mixed together.
    

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24. The cunning challenges of contexts
    

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25. concept
    
    
    of
    
    
    context
    Ecto
    business
    logic
    juggler by Orin zuu from the Noun Project
    The cunning challenges of contexts
    

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26. The cunning challenges of contexts
    • Different layers of concerns are mixed together.
    
    
    • Relationships between components are ambiguous.
    

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27. from Phoenix of
    fi
    cial guide
    “Sometimes it may be tricky to determine if two resources
    belong to the same context or not. In those cases, prefer
    distinct contexts per resource and refactor later if necessary. “
    The cunning challenges of contexts
    

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28. Outline
    • The cunning challenges of contexts
    
    
    • The quest, and what did not work
    
    
    • Build-your-own architecture
    
    
    • Revisit contexts
    
    
    • Context-driven development
    

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29. What to do with context?
    • Look at open-source projects?
    

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30. What to do with context?
    • Look at open-source projects?
    
    
    • Domain Driven Design?
    

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31. source: https://youtu.be/tMO28ar0lW8
    

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32. https://gfycat.com/elderlyhatefulhornet
    Challenge accepted.
    

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33. https://www.domainlanguage.com/wp-content/uploads/2016/05/DDD_Reference_2015-03.pdf
    

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35. https://gfycat.com/composedimportantavians
    

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36. 💡
    

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37. https://gph.is/g/4zqknpn?tc=1 via @giphy
    architecture
    

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38. from Phoenix of
    fi
    cial guide
    “Contexts are dedicated modules that
    
    
    expose and group related functionality.“
    

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39. Outline
    • The cunning challenges of contexts
    
    
    • The quest, and what did not work
    
    
    • Build-your-own architecture
    
    
    • Revisit contexts
    
    
    • Context-driven development
    

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40. How do I build an application?
    

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41. Use case
    Adapter
    Infrastructure
    Domain
    

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42. Adapter
    Infrastructure
    Domain
    Use case
    • Business logic
    
    
    • Free of technology
    

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43. Use case
    Adapter
    Infrastructure
    Domain
    • Use case orchestration
    
    
    • Transaction management
    

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44. Use case
    Adapter
    Infrastructure
    Domain
    • Translation
    

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45. Use case
    Adapter
    Infrastructure
    Domain
    • External dependency
    
    • Technical details
    

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46. Adapter
    Use case
    Infrastructure
    Domain
    

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47. Clean architecture file structure
    lib
    
    
    ├── domain
    
    
    ├── use_case
    
    
    ├── adapter
    
    
    └── infrastructure
    

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48. Clean architecture file structure
    lib
    
    
    ├── domain
    
    
    ├── use_case
    
    
    ├── adapter
    
    
    └── infrastructure
    ├── model
    
    
    ├── store (interface)
    
    
    └── service
    
    
    

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49. Clean architecture file structure
    lib
    
    
    ├── domain
    
    
    ├── use_case
    
    
    ├── adapter
    
    
    └── infrastructure
    ├── upload_image.ex
    
    
    └── register_user.ex
    
    
    

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50. Clean architecture file structure
    lib
    
    
    ├── domain
    
    
    ├── use_case
    
    
    ├── adapter
    
    
    └── infrastructure
    ├── cli.ex
    
    
    ├── web
    
    
    └── store
    

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51. Clean architecture file structure
    lib
    
    
    ├── domain
    
    
    ├── use_case
    
    
    ├── adapter
    
    
    └── infrastructure
    ├── cli.ex
    
    
    ├── web
    
    
    └── store
    

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52. Clean architecture file structure
    lib
    
    
    ├── domain
    
    
    ├── use_case
    
    
    ├── adapter
    
    
    └── infrastructure
    ├── cli.ex
    
    
    ├── web
    
    
    └── store
    

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53. Clean architecture file structure
    lib
    
    
    ├── domain
    
    
    ├── use_case
    
    
    ├── adapter
    
    
    └── infrastructure
    ├── application.ex
    
    
    ├── mailer.ex
    
    
    ├── repo.ex
    
    
    ├── web
    
    
    ├── endpoint.ex
    
    
    ├── gettext.ex
    
    
    ├── router.ex
    
    
    └── telemetry.ex
    

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54. (Revisit) The cunning challenges of contexts
    • Different layers of concerns are mixed together.
    
    
    • Relationships between components are ambiguous.
    

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55. • Different layers of concerns are mixed together.
    
    
    Separation of concerns 👍
    
    
    • Relationships between components are ambiguous.
    

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56. • Different layers of concerns are mixed together.
    
    
    Separation of concerns 👍
    
    
    • Relationships between components are ambiguous.
    
    
    Clear relationship between components 👍
    

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57. • Different layers of concerns are mixed together.
    
    
    Separation of concerns 👍
    
    
    • Relationships between components are ambiguous.
    
    
    Clear relationship between components 👍
    
    
    • Very testable 👍
    

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58. The almighty clean architecture
    • Separation of concerns
    
    
    • Clear relationship between components
    
    
    • Very testable
    

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59. https://media.giphy.com/media/jQnrJSmFB6KVQ7kfpK/giphy.gif
    

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60. Outline
    • The cunning challenges of contexts
    
    
    • The quest, and what did not work
    
    
    • Build-your-own architecture
    
    
    • Revisit contexts
    
    
    • Context-driven development
    

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61. from Phoenix of
    fi
    cial guide
    “Contexts are dedicated modules that
    
    
    expose and group related functionality.“
    

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62. How can context improve
    
    
    our current architecture?
    

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63. Example: User noti
    fi
    cation
    Use case
    Adapter
    Infrastructure
    Domain
    

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64. Adapter
    Infrastructure
    Domain
    Use case
    • model/noti
    fi
    cation.ex
    
    
    • store/noti
    fi
    cation_store.ex
    
    
    • store/user_store.ex
    Example: User noti
    fi
    cation
    

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65. Use case
    Adapter
    Infrastructure
    Domain
    • notify_user.ex
    Example: User noti
    fi
    cation
    

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66. Use case
    Adapter
    Infrastructure
    Domain
    • store/user_store.ex
    
    
    • store/noti
    fi
    cation_store.ex
    
    
    • web/controller/
    
    
    noti
    fi
    cation_controller.ex
    Example: User noti
    fi
    cation
    

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67. Improve current architecture with context
    • domain/model/noti
    fi
    cation.ex
    
    
    • domain/store/noti
    fi
    cation_store.ex
    
    
    • domain/store/user_store.ex
    
    
    • use_case/notify_user.ex
    
    
    • adapter/store/noti
    fi
    cation_store.ex
    
    
    • adapter/store/user_store.ex
    
    
    • adapter/web/controller/noti
    fi
    cation_controller.ex
    

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68. • domain/model/noti
    fi
    cation.ex
    
    
    • domain/store/noti
    fi
    cation_store.ex
    
    
    • domain/store/user_store.ex
    
    
    • use_case/notify_user.ex
    
    
    • adapter/store/noti
    fi
    cation_store.ex
    
    
    • adapter/store/user_store.ex
    
    
    • adapter/web/controller/noti
    fi
    cation_controller.ex
    Improve current architecture with context
    

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69. • domain/model/noti
    fi
    cation.ex
    
    
    • domain/model/user.ex
    
    
    • domain/store/noti
    fi
    cation_store.ex
    
    
    • domain/store/user_store.ex
    
    
    • use_case/notify_user.ex
    
    
    • adapter/store/noti
    fi
    cation_store.ex
    
    
    • adapter/store/user_store.ex
    
    
    • adapter/web/controller/noti
    fi
    cation_controller.ex
    Improve current architecture with context
    

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70. • domain/model/noti
    fi
    cation.ex
    
    
    • domain/model/user.ex
    
    
    • domain/store/noti
    fi
    cation_store.ex
    
    
    • domain/store/user_store.ex
    
    
    • use_case/notify_user.ex
    
    
    • adapter/store/noti
    fi
    cation_store.ex
    
    
    • adapter/store/user_store.ex
    
    
    • adapter/web/controller/noti
    fi
    cation_controller.ex
    Improve current architecture with context
    

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71. Adapter
    Use case
    Infrastructure
    Domain
    

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72. Adapter
    Use case
    Infrastructure
    Domain
    

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73. Apply context
    Adapter Use case
    Infrastructure Domain
    

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74. Apply contexts
    Adapter Use case
    Infrastructure Domain
    External Internal
    

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75. Apply contexts
    Adapter Use case
    Infrastructure Domain
    External Internal
    

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76. Apply contexts
    Internal
    Use case
    Domain
    

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77. Apply contexts
    Internal
    Use case
    Domain
    Context
    

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78. Apply contexts
    Use case
    Domain
    Context YourApp.[Context]
    YourApp.[Context].[UseCase]
    YourApp.[Context].[Domain]
    

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79. Apply contexts
    Use case
    Domain
    Context Noti
    fi
    cation
    
    Noti
    fi
    cation.notify_user
    
    Noti
    fi
    cation.Noti
    fi
    cation
    
    Noti
    fi
    cation.UserStore
    
    Noti
    fi
    cation.Noti
    fi
    cationStore
    

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80. Apply contexts
    Use case
    Domain
    Context Noti
    fi
    cation
    Noti
    fi
    cation.notify_user
    
    Noti
    fi
    cation.Noti
    fi
    cation
    
    Noti
    fi
    cation.UserStore
    
    Noti
    fi
    cation.Noti
    fi
    cationStore
    

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81. Apply contexts
    Use case
    Domain
    Context Noti
    fi
    cation
    Noti
    fi
    cation.notify_user
    Noti
    fi
    cation.Noti
    fi
    cation
    
    Noti
    fi
    cation.UserStore
    
    Noti
    fi
    cation.Noti
    fi
    cationStore
    

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82. Apply contexts
    Use case
    Domain
    Context Noti
    fi
    cation
    Noti
    fi
    cation.notify_user
    Noti
    fi
    cation.Noti
    fi
    cation
    Noti
    fi
    cation.UserStore
    
    Noti
    fi
    cation.Noti
    fi
    cationStore
    

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83. File structure
    ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    
    
    

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84. File structure
    ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    
    
    # context
    

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85. ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    File structure
    

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86. ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    File structure
    

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87. ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    File structure
    

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88. ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    File structure
    

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89. ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    File structure
    

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90. ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    File structure
    

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91. ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    File structure
    

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92. ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    File structure
    

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93. ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    File structure
    

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94. ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    File structure
    

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95. ElixirLab
    Noti
    fi
    cation
    Account
    Cross-context relationship
    

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96. ElixirLab
    Noti
    fi
    cation
    Account
    Account.create_user Noti
    fi
    cation.not
    fi
    y_new_user
    Cross-context relationship
    

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97. ElixirLab
    Noti
    fi
    cation
    Account
    Cross-context relationship: Implicit dependency?
    depends on
    

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98. ElixirLab
    Noti
    fi
    cation
    Account
    Cross-context relationship
    depends on depends on
    

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99. ├── noti
    fi
    cation
    
    
    │ ├── noti
    fi
    cation.ex
    
    
    │ ├── noti
    fi
    cation_store.ex
    
    
    │ └── user_store.ex
    
    
    └── noti
    fi
    cation.ex
    The external layer
    

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100. elixir_lab
     
     
     ├── noti
     fi
     cation
     
     
     │ ├── noti
     fi
     cation.ex
     
     
     │ ├── noti
     fi
     cation_store.ex
     
     
     │ └── user_store.ex
     
     
     └── noti
     fi
     cation.ex
     The external layer
     

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101. elixir_lab
     
     
     ├── noti
     fi
     cation
     
     
     │ ├── noti
     fi
     cation.ex
     
     
     │ ├── noti
     fi
     cation_store.ex
     
     
     │ └── user_store.ex
     
     
     └── noti
     fi
     cation.ex
     elixir_lab_external
     
     
     ├── noti
     fi
     cation_store.ex
     
     
     ├── repo
     
     
     │ ├── schema
     
     
     │ └── user_repo.ex
     
     
     ├── web (Phoenix)
     The external layer
     

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102. elixir_lab
     
     
     ├── noti
     fi
     cation
     
     
     │ ├── noti
     fi
     cation.ex
     
     
     │ ├── noti
     fi
     cation_store.ex
     
     
     │ └── user_store.ex
     
     
     └── noti
     fi
     cation.ex
     elixir_lab_external
     
     
     ├── noti
     fi
     cation_store.ex
     
     
     ├── repo
     
     
     │ ├── schema
     
     
     │ └── user_repo.ex
     
     
     ├── web (Phoenix)
     The external layer
     

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103. • Separation of concerns
     
     
     • Clear relationship between components
     
     
     • Very testable
     Result of applying context
     

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104. • Separation of concerns
     
     
     • Clear relationship between components
     
     
     • Very testable
     
     
     • Groups related functionality together 👍
     Result of applying context
     

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105. Outline
     • The cunning challenges of contexts
     
     
     • The quest, and what did not work
     
     
     • Build-your-own architecture
     
     
     • Revisit contexts
     
     
     • Context-driven development 🏁
     

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106. Context-driven development
     • Separate your business concerns.
     

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107. Context-driven development
     • Separate your business concerns.
     
     
     • Take advantage of Elixir’s
     fl
     exibility.
     

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108. Context-driven development
     • Separate your business concerns.
     
     
     • Take advantage of Elixir’s
     fl
     exibility.
     
     
     • But use it carefully.
     

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109. Context-driven development
     • Separate your business concerns.
     
     
     • Take advantage of Elixir’s
     fl
     exibility.
     
     
     • But use it carefully.
     
     
     • Make your architecture scream.
     

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110. source: https://tenor.com/view/chubby-chubby-cat-stuck-door-pet-door-gif-5518148
     Phoenix Your application
     

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111. source: http://gph.is/1eeJ98k?tc=1
     Phoenix Your application
     

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112. Resources
     Books
     • Clean Architecture: A Craftsman's Guide to Software Structure by
     Robert C. Martin
     
     
     • Functional Web Development with Elixir, OTP, and Phoenix by by
     Lance Halvorsen
     
     
     • Domain Modeling Made Functional by Scott Wlaschin
     
     
     • Implementing Domain-Driven Design by Vaughn Vernon
     
     
     • Programming Phoenix by Bruce Tate, Chris McCord and José Valim
     

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113. Resources
     Videos
     • Building Beautiful Systems with Phoenix Contexts and DDD by
     Andrew Hao
     
     
     • Lonestar ElixirConf 2017- KEYNOTE: Phoenix 1.3 by Chris McCord
     
     
     • Ruby Midwest 2011 - Keynote: Architecture the Lost Years by
     Robert Martin
     

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114. Resources
     Articles / Blog posts / Forum questions
     • https://hexdocs.pm/phoenix/contexts.html
     
     
     • https://elixirforum.com/t/hexagonal-architecture-in-elixir/32225/16
     
     
     • https://elixirforum.com/t/how-to-determine-contexts-with-phoenix-1-3/4367
     
     
     • https://aaronrenner.io/2019/09/18/application-layering-a-pattern-for-extensible-
     elixir-application-design.html
     
     
     • https://www.destroyallsoftware.com/screencasts/catalog/functional-core-
     imperative-shell
     
     
     • https://blog.cleancoder.com
     

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115. https://github.com/jenny-codes/elixirlab
     @jenny_codes
     

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