Code Smell 17 - Global Functions

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());
    }
}

Right

<?

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

Detection

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

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.

Singleton: The Root of all Evil

Maxi Contieri ・ Nov 17 '20

#oop #tutorial #codenewbie #programming

More Info

Wikipedia

Credits

Photo by Mae Mu on Unsplash

The road to programming hell is paved with global variables.

Steve McConnell

Software Engineering Great Quotes

Maxi Contieri ・ Dec 28 '20

#codenewbie #programming #quotes #software

This article is part of the CodeSmell Series.

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Maxi Contieri ・ May 21 '21

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Last update: 2021/06/26