Code Smell 27 - Associative Arrays

Code Smell 27 - Associative Arrays

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[Key, values], magic, fast, malleable and error prune.

TL;DR: Use arrays for rapid prototyping, use object for serious business.

Problems

  • Coupling

  • Information Hiding

  • Code Duplication

  • Fail Fast

  • Integrity

Solutions

  1. Reify objects

  2. Create cohesive small objects

  3. Don't leave them anaemic, find their cohesive relations.

Sample Code

Wrong

<?

$coordinate = array('latitude'=>1000, 'longitude'=>2000); 
//Its OK. they are just arrays. a Bunch of raw data

Anaemic

<?

final class GeographicCoordinate {

    function __construct($latitude, $longitude) {
        $this->longitude = $longitude;
        $this->latitude = $latitude;
    }
}

$coordinate = new GeographicCoordinate(1000, 2000);
//should throw an error since these values don't exist on Earth

Validated

<?

final class GeographicCoordinate {

    function __construct($latitude, $langitude) {
        if (!$this->isValidLatitude($latitude)) {
            throw new InvalidLatitudeException($latitude);
            //...
            $this->longitude = $longitude;
            $this->latitude = $latitude;
        }
    }
}

$coordinate = new GeographicCoordinate(1000, 2000);
//trows an error since these values don't exist on Earth

Degrees deserves reification

<?

final class Latitude {
    function __construct($degrees) {
        if (!$degrees->between(-90, 90)) {
            throw new InvalidLatitudeException($latitude);
        }
        //...
    }
}

Many people suffer from primitive obsession and believe this is over design. Designing software is about making decisions and comparing trade-offs. The performance argument is not valid nowadays since modern virtual machines can efficiently deal with small short-lived objects.

<?

final class GeographicCoordinate {

    function distanceTo(GeographicCoordinate $coordinate) {
    }

    function pointInPoligon(Polygon $polygon) {
        //....
    }
}

//Now we are in geometry world (and not in array world anymore). we can safely do many exciting things.

Detection

We cannot forbid Associative Arrays since they are very good as a first approach.

They will be fine for exporting data, serialization, persistence and other accidental implementation issues.

We should avoid them on our systems.

Tags

  • Primitive

Conclusion

When creating objects, we must not think of them as data. This is a common misconception.

We should stay loyal to our Bijection and discover real world objects.

Most associative arrays have cohesion and represent real world entities, and we must treat them as first class objects.

Relations

Credits

Photo by Melissa Askew on Unsplash


There’s nothing more permanent than a temporary hack.

Kyle Simpson


This article is part of the CodeSmell Series.

Last update: 2021/09/24

 
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