Code Smell 32 - Singletons

The most used and (in)famous design pattern in the world is causing us great harm.

Problems

• Coupling

• Testability

• Accidental implementation problems.

• Multi threading issues.

• Static methods polluting.

• Object creation contract violation.

• Bijection mismatch.

• Memory issues.

• Premature Optimization.

Code Smell 20 - Premature Optimization

Maxi Contieri ・ Nov 8 '20

#oop #developing #coding #codesmell

Solutions

1. Avoid it.

2. Use contextual unique objects.

3. Benchmark object creation.

Examples

• Database Access

• Globals

• Loggers

• Helpers

Code Smell 22 - Helpers

Maxi Contieri ・ Nov 12 '20

#oop #helpers #codenewbie #beginners

Sample Code

Wrong

God is the archetypical singleton example.

Right

Detection

This is a design pattern. We should avoid it by policy.

We can add linter rules for patterns like 'getInstance()' so new developers cannot infect code with this anti-pattern.

Tags

• Globals

Conclusion

This is an historical mistake already acknowledged by the community. Nevertheless, lazy developers bring it again and again. We need to reach a consensus on its drawbacks.

Relations

Code Smell 06 - Too Clever Programmer

Maxi Contieri ・ Oct 25 '20

#codenewbie #tutorial #beginners

Code Smell 25 - Pattern Abusers

Maxi Contieri ・ Nov 15 '20

#oop #tutorial #programming #patterns

Code Smell 18 — Static Functions

Maxi Contieri ・ Nov 6 '20

#codenewbie #tutorial #development #coding

More info

Singleton: The Root of all Evil

Maxi Contieri ・ Nov 17 '20

#oop #tutorial #codenewbie #programming

Credits

Photo by Maria Teneva on Unsplash

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The Diagram is Not the Model. The model is not the diagram. It is an abstraction, a set of concepts and relationships between them.

Eric Evans

Comments

[Junxiao Shi]

How is GodFactory supposed to be used if it always throws?

[Maxi Contieri]

Hi. I changed the example and removed factory usage since I think it was a bit confusing