Magic functions that can receive a lot of different (and not polymorphic arguments)

TL;DR: Create a clear contract. Expect just one protocol.

Problems

• Fail Fast principle violation

• Error prune

• Readability

• If polluting

• Nulls

• Bad Cohesion

Solutions

1. Take just one "kind" of input

2. Arguments should adhere to a single protocol.

Sample Code

Wrong

<?

function parseArguments($arguments) {
    $arguments = $arguments ?: null;
    //Always the billion-dollar mistake
    if (is_empty($arguments)) {
        $this->arguments = http_build_query($_REQUEST);
        //Global coupling and side effects
    } elseif (is_array($arguments)) {
        $this->arguments = http_build_query($arguments);
    } elseif (!$arguments) { //null unmasked
        $this->arguments = null;
    } else {
        $this->arguments = (string)$arguments;
    }
}

Right

<?

function parseArguments(array $arguments) {
    $this->arguments = $arguments;
    //much cleaner, isn't it ?
}

Detection

We can detect this kind of method when they do different things, asking for the argument kind.

Tags

• If Polluter

Conclusion

Magic castings and flexibility have a price. They put the rubbish under the rug and violate the fail fast principle.

Relations

Credits

Photo by Hennie Stander on Unsplash

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Referential transparency is a very desirable property: it implies that functions consistently yield the same results given the same input, irrespective of where and when they are invoked.

Edward Garson

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This article is part of the CodeSmell Series.