# Code Smell 27 - Associative Arrays

*[Key, values], magic, fast, malleable and error prone.*

> 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 

[Gist Url]: # (https://gist.github.com/mcsee/ff148550e3d2018c2ee345ea0790e8fc)
```php
<?

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

### Anaemic

[Gist Url]: # (https://gist.github.com/mcsee/1ac19d1af240d28a59c01134cd487b7e)
```php
<?

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

[Gist Url]: # (https://gist.github.com/mcsee/4753e242da21027d2a8e7243de877250)
```php
<?

final class GeographicCoordinate {

    function __construct($latitude, $longitude) {
        if (!$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
```

## Right

### Degrees deserves reification

[Gist Url]: # (https://gist.github.com/mcsee/33f84258133eb9bafbac1f85532527c6)
```php
<?

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

*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.*

[Gist Url]: # (https://gist.github.com/mcsee/9f7c55093672a63ec8c89ca24b9a7277)
```php
<?

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](https://maximilianocontieri.com/the-one-and-only-software-design-principle) 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

%[https://maximilianocontieri.com/code-smell-01-anemic-models]

%[https://maximilianocontieri.com/fail-fast]

%[https://maximilianocontieri.com/refactoring-012-reify-associative-arrays]

# Credits

Photo by <a href="https://unsplash.com/@melissaaskew">Melissa Askew</a> on <a href="https://unsplash.com/s/photos/group">Unsplash</a>

* * *

> There’s nothing more permanent than a temporary hack.

_Kyle Simpson_ 

%[https://maximilianocontieri.com/software-engineering-great-quotes]

* * *

This article is part of the CodeSmell Series.

%[https://maximilianocontieri.com/how-to-find-the-stinky-parts-of-your-code]