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Code Smell 17 - Global Functions

Maxi Contieri
Learn something new every day. - I am a senior software engineer working in industry, teaching and writing on software design, SOLID principles, DDD and TDD.
Originally published at maximilianocontieri.com Updated on ・1 min read

Discouraged by Object-Oriented Programmings, Many mixed languages support it. And developers abuse them.

TL;DR: Global function bring a lot of coupling. Don't use them.

Problems

  • Coupling

  • Readability

  • Maintainability

  • Testability

Solutions

  • Wrap the function in a context object.

Examples

  • External Resources Access, Database access, Time and Operating System resources.

Sample Code

Wrong

<?

class Employee {
    function taxesPayedUntilToday() {
        return database()->select(
            "SELECT TAXES FROM EMPLOYEE".
            " WHERE ID = " . $this->id() .
            " AND DATE < " . currentDate());
    }
}
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Right

<?

final class EmployeeTaxesCalculator {
    function taxesPayedUntilToday($context) {
        return $context->SelectTaxesForEmployeeUntil(
            $this->ssn,
            $context->currentDate());
    }
}
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Detection

Many modern languages avoid them. For the permissive ones, scope rules can be applied and automatically checked.

Tags

  • Global

Conclusion

Structured programming considers global functions harmful. Yet, we can observe some bad practices cross paradigm boundaries.

Relations

  • Singleton and Classes are global points of access.

More Info

Credits

Photo by Mae Mu on Unsplash


The road to programming hell is paved with global variables.

Steve McConnell


This article is part of the CodeSmell Series.

Last update: 2021/06/26

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