Mutation is good. Things change

TL;DR: Don't change essential attributes or behavior

Problems

• Bijection violation

• Mutability

• Ripple Effect

Solutions

1. Protect essential attributes from change.

2. Remove setters

Refactorings

Context

Heraclitus said:

“No man ever steps in the same river twice. For it’s not the same river and he’s not the same man.”

The man stays the same in essence. But his body evolves.

Sample Code

Wrong

const date = new Date();
date.setMonth(4);

Right

const date = new Date("2022-03-25");

Detection

[X] Manual

This is a semantic smell. We need to model which attributes/behaviors are essential and which are accidental.

Tags

• Mutability

Conclusion

We need to favor immutable objects.

Objects can mutate in accidental ways, not in essential ones.

Relations

More Info

Disclaimer

Code Smells are just my opinion.

Credits

Photo by Nick Fewings on Unsplash

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Changes in software design will eventually mean "one step forward, two steps back". It is inevitable.

Salman Arshad

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This article is part of the CodeSmell Series.