Magic Strings & Magic Numbers 🪄

Magic numbers are literal numeric values that are used in code without any explanation of their meaning. Magic strings are strings literals without any explanation either.

Why is it a problem ?

First of all, it is not easy to read when there is only a number that is written in code. Let's look at an example:

$myModel = new Model();
$myModel->status_id = 3; // A magic number
$myModel->save();

Here there is no explanation of the meaning behind the value "3". I can probably find the answer by looking at the code surrounding this snippet or look for a corresponding value elsewhere (like in a database table).

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Also the number "3" is not important in itself for my comprehension of the code. The status should correspond to a more realistic status of my business like "Created", "Sent", "Archived".

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The same applies to Magic Strings:

switch ($request->code_response) {
  case "code_1": // Magic String
    doAnAction();
    break;
  case "code_2": // Also a Magic String
    doAnotherAction();
    break;
...

I can probably guess the utility of these code values by looking at the code of the doAnAction() and doAnotherAction() functions but it would greatly help to have a code more readable at this stage.

How to solve this problem ?

Different solutions can be used. The simplest one is to use a named variable:

$statusCreated = 3;

$myModel = new Model();
$myModel->status_id = $statusCreated;
$myModel->save();

A better solution is to use constant values in a separate class or even an enum.

enum MyModelStatuses {
...
  case CREATED = 3;
  case ARCHIVED = 4;
...
}

$myModel = new Model();
$myModel->status_id = MyModelStatuses::CREATED->value; // don't forget to import the new class
$myModel->save();

A separate class allow you to have a global logic behind these values that can be reused elsewhere.

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Another solution when the Magic Number is only used in one class is to use a const variable in the class:
From:

class MyClass {
  public function myFunction() {
    for ($i = 0; $i < 10; $i++) { // Here 10 is a Magic Number
      // Do something
    }
  }
}

To:

class MyClass {
  private const NUMBER_OF_ITERATIONS = 10;

  public function myFunction() {
    for ($i = 0; $i < self::NUMBER_OF_ITERATIONS; $i++) {
      // Do something
    }
  }
}

Such constants are used as parameters inside your class and can be easily replaced by new values.

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Let's see a last use case of avoiding Magic Numbers.

$myModel = new MyModel();
$myModel->duration = 60; // Magic Number
$myModel->save();

Here the value 60 can be confusing. What is its unit ? It could me seconds, it could be minutes or even hours !

$secondsInAMinute = 60;

$myModel = new MyModel();
$myModel->duration = $secondsInAMinute;
$myModel->save();

The name of the new variable itself helps to make the code readable. Also the same number could refer to different meanings (in this case we could have 60 as $minutesInAnHour somewhere else in the code).

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That's it ! I hope that this article helped you understand what are Magic Numbers (and Magic Strings) and how to remove them from your code !