Code Smell 13 — Empty Constructors

Incomplete objects cause lots of issues.

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Problems

• Mutability
• Incomplete objects
• Concurrency inconsistencies between creation and essence setting.
• Setters

Nude Models — Part I : Setters

Solutions

• Pass the object’s essence on creation

The evil powers of mutants

Examples

• Some persistence frameworks in static typed languages require an empty constructor.

Exceptions

• Stateless objects. Always better solution than static class methods.

Sample Code

Wrong

Right

Detection

Any linter can warn this (possible) situation.

Tags

• Essence
• Incomplete
• Mutable

Conclusion

Always create complete objects. Make their essence immutable to endure through time. Every object needs its essence to be a valid one since inception.

Writing a class without its contract would be similar to producing an engineering component (electrical circuit, VLSI (Very Large Scale Integration) chip, bridge, engine…) without a spec. No professional engineer would even consider the idea.

Bertrand Meyer

Software Engineering Great Quotes

This article is part of the CodeSmell Series.

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