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Code Smell 50 - Object Keys

Maxi Contieri
Learn something new every day. - I am a senior software engineer working in industry, teaching and writing on software design, SOLID principles, DDD and TDD.
・2 min read

Primary keys, IDs, references. The first attribute we add to our objects. They don't exist in the real world.

Problems

Solutions

  1. Reference object to objects.

  2. Build a MAPPER.

  3. Only use keys if you need to provide an external (accidental) reference. Databases, APIs, Serializations.

  4. Use dark keys or GUIDs when possible.

  5. If you are afraid of getting a big relation graph use proxies or lazy loading.

  6. Don't use DTOs.

Sample Code

Wrong

Right

Detection

This is a design policy.

We can enforce business objects to warn us if we define an attribute or function including the sequence id.

Tags

  • Accidental

Conclusion

Ids are not necessary for OOP. You reference objects (essential) and never ids (accidental).

In case you need to provide a reference out of your system's scope (APIs, interfaces, Serializations) use dark and meaningless IDs (GUIDs).

Relations

More info

Credits

Photo by Maurice Williams on Unsplash


All problems in computer science can be solved by another level of indirection.

David Wheeler

Discussion (2)

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frankfont profile image
Frank Font

Simple answers don't always fit complex problems.
Semantic keys are not always a code smell in the wild.
I've found the lack of them when needed for performance and scale resilience can be a problem. They are the first thing I sniff for in a relational database and some shared object structures.

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mcsee profile image
Maxi Contieri Author

Of course. But then we are talking about data and performance(accidental) In my article I was focusing solely on behaviour (essential)