Non-Parameterized constructors are a code smell of an invalid object that will dangerously mutate. Incomplete objects cause lots of issues.
TL;DR: Pass the essence to all your objects so they will not need to mutate.
Problems
Solutions
Pass the object's essence on creation
Create objects with their immutable essence.
Refactorings ⚙️
https://maximilianocontieri.com/refactoring-001-remove-setters
https://maximilianocontieri.com/refactoring-016-build-with-the-essence
Examples
- Some persistence frameworks in static typed languages require an empty constructor.
Sample Code
Wrong
class AirTicket {
constructor() {
}
}
Right
class AirTicket {
constructor(origin,
destination,
arline,
departureTime,
passenger) {
// ...
}
}
Detection
Any linter can warn this (possible) situation.
Exceptions
Level
[X] Beginner
Why the Bijection Is Important
In the MAPPER, objects correspond to real-world entities.
Real people aren't born nameless and formless, then gradually acquire attributes.
You don't meet someone who temporarily has no age or email address.
When you model a person, you should capture their essential attributes at birth, just like reality.
Breaking this bijection by creating hollow objects forces you to represent impossible states.
Empty constructors create phantom and invalid objects that don't exist in your domain model, violating the mapping between your code and reality.
AI Generation
AI code generators frequently produce this smell because they often follow common ORM patterns.
When you prompt AI to "create a Person class," it typically generates empty constructors with getters and setters.
AI tools trained on legacy codebases inherit these patterns and propagate them unless you explicitly request immutable objects with required constructor parameters.
AI Detection
AI tools can detect and fix this smell when you provide clear instructions.
You need to specify that objects should be immutable with required constructor parameters.
Without explicit guidance, AI tools may not recognize empty constructors as problematic since they appear frequently in training data.
Try Them!
Remember: AI Assistants make lots of mistakes
Suggested Prompt: Create an immutable class with required information. Include constructor validation and no setters. Make all fields final and use constructor parameters only
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.
We should read Plato's ideas about immutability and create entities in a complete and immutable way.
These immutable objects favor bijection and survive the passing of time.
Relations ❤️
https://coderlegion.com/7246/code-smell-01-anemic-models
https://maximilianocontieri.com/code-smell-28-setters
https://maximilianocontieri.com/code-smell-40-dtos
https://coderlegion.com/8662/code-smell-10-too-many-arguments
https://maximilianocontieri.com/code-smell-116-variables-declared-with-var
https://codexposed.hashnode.dev/constructors-demystified
https://coderlegion.com/6742/the-evil-power-of-mutants
https://coderlegion.com/8662/code-smell-10-too-many-arguments
Credits
Photo by Brett Jordan in Pexels
In a purely functional program, the value of a [constant] never changes, and yet, it changes all the time! A paradox!
Joel Spolski
https://maximilianocontieri.com/software-engineering-great-quotes
This article is part of the CodeSmell Series.
https://maximilianocontieri.com/how-to-find-the-stinky-parts-of-your-code