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Cover image for Code Smell 15 - Missed Preconditions

Code Smell 15 - Missed Preconditions

mcsee profile image Maxi Contieri Originally published at mcsee.Medium Updated on ・1 min read

Assertions, Preconditions, Postconditions and invariants are our allies to avoid invalid objects. Avoiding them leads to hard-to-find errors.

Problems

  • Consistency
  • Contract breaking
  • Hard to debug
  • Bad cohesion

Solutions

  • Create strong preconditions
  • Raise exceptions
  • Fail Fast
  • Defensive Programming

Examples

  • Constructors are an excellent first line of defense

  • Anemic Objects lack these rules.

Sample Code

Wrong

Right

Detection

  • It's difficult to find missing preconditions, as long with assertions and invariants.

Tags

  • Consistency

Conclusion

Always be explicit on object integrity.

Turn on production assertions.

Even if it brings performance penalties.

Data and object corruption is harder to find.

Fail fast is a blessing.

%[https://mcsee.hashnode.dev/fail-fast]

More info

Relations

Credits

Photo by Jonathan Chng on Unsplash


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

%[https://mcsee.hashnode.dev/software-engineering-great-quotes]

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