DDD Antipatterns - Speaker Deck

DDD Antipatterns

by resotto

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DDD Antipatterns Avoiding Costly Mistakes of DDD Programming

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About me - Software Engineer - I like Sushi. https://github.com/resotto https://twitter.com/resotto3 © 2016 Side Project. CC BY 3.0 https://www.iconfinder.com/iconsets/colorful-guache-social-media-logos-1

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Index - Old Schema - [WIP] Thick Application Service - [WIP] Non-Operating Factory - [WIP] Insufficient Refactoring - [WIP] Pending Absorption of Domain Knowledge

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Old Schema

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Antipattern Using the old table schema as it is As Is To Be

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Antipattern Using the old table schema as it is As Is To Be

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Why? Because Domain Model depends on the old table schema by reversing the direction of dependency. Robert C. Martin Clean Architecture

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Robert C. Martin Clean Architecture

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Robert C. Martin Clean Architecture

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Robert C. Martin Clean Architecture

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How to find it? Following conversation would be taken place: I feel writing DTOs is so hard. (How) Can I use remaining tables with DDD? © 2017 Iconika. CC BY 3.0 https://www.iconfinder.com/iconsets/social-productivity

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How to find it? Following conversation would be taken place: I feel writing DTOs is so hard. (How) Can I use remaining tables with DDD? Domain Model properties can’t help but look like table columns. © 2017 Iconika. CC BY 3.0 https://www.iconfinder.com/iconsets/social-productivity

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When to be acceptable? When properties of the Domain Model correspond to columns of remaining tables consequently Domain Model

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When to be acceptable? When properties of the Domain Model correspond to columns of remaining tables consequently Domain Model As Is © 2014 Hard Task. CC BY 3.0 https://www.iconfinder.com/iconsets/arrow-5

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When to be acceptable? When properties of the Domain Model correspond to columns of remaining tables consequently Domain Model This Order! As Is © 2014 Hard Task. CC BY 3.0 https://www.iconfinder.com/iconsets/arrow-5

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What if you have to use old schema? It might be impossible to replace an application with DDD. https://www.iconfinder.com/iconsets/social-productivity-1 © 2017 Iconika. CC BY 3.0 https://www.iconfinder.com/iconsets/arrows-107

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What if you have to use old schema? It might be impossible to replace an application with DDD. © 2017 Iconika. CC BY 3.0 https://www.iconfinder.com/iconsets/arrows-107 https://www.iconfinder.com/iconsets/social-productivity-1

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Domain Model

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As Is If Domain Model properties don’t correspond to the old table columns... Domain Model And do I have to add “name” to Domain Model??? © 2014 Hard Task. CC BY 3.0 https://www.iconfinder.com/iconsets/arrow-5

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As Is If Domain Model properties don’t correspond to the old table columns... Domain Model Oops! “weight” can’t be stored! And do I have to add “name” to Domain Model??? © 2014 Hard Task. CC BY 3.0 https://www.iconfinder.com/iconsets/arrow-5 © 2017 Iconika. CC BY 3.0 https://www.iconfinder.com/iconsets/social-productivity

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Solution Making up new table schema As Is To Be

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Solution Making up new table schema As Is To Be

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Old Schema - Purpose: replacing an application with DDD - Antipattern: using the old table schema as it is - Why: because of reversing dependency - Solution: making up new table schema Wrap Up!

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Thank you!