Code Smell 35 - State as Properties

Code Smell 35 - State as Properties

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When an object changes its state the best solution is to change the attribute, isn't it?

Problems

  • Mutability

  • Attributes polluting

  • Setters

Solutions

1 - Model states as mathematical set inclusion.

2 - State is accidental, take it away from the object.

Examples

  • State diagrams

Sample Code

Wrong

Detection

If we want to be extreme, we should consider every setter to be a potential state change. Linters can warn us. But we might end up getting too many false positives.

Exceptions

  • Over Design

  • Performance issues (if a serious benchmark supports it).

Tags

  • Mutation

Conclusion

This technique is very elegant but can lead to over design. For example changing a visual component its color should be a counterexample to this smell.

We should be aware and very caution like with any other smell.

They are hints and not rigid rules.

Relations

More info

Credits

Photo by Tom Crew on Unsplash


First make the change easy (warning: this might be hard), then make the easy change.

Kent Beck


This article is part of the CodeSmell Series.

 
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