Enums - An introduction

Transcript

1. Tommy Mühle | tommy-muehle.io
   Enums
   An introduction
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2. Tommy Mühle | tommy-muehle.io
   Tommy Mühle

   Software Engineer and Author
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3. Tommy Mühle | tommy-muehle.io
   What is an enum?
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4. Tommy Mühle | tommy-muehle.io
   Tommy Mühle | tommy-muehle.io
   … a data type consisting of a set of
   named values called elements …
   of the type.
   

   The enumerator names are
   usually identifiers that behave
   as constants in the language.
   https:/
   /en.wikipedia.org/wiki/Enumerated_type
   

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5. Tommy Mühle | tommy-muehle.io
   How they are
   implemented in PHP?
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6. Tommy Mühle | tommy-muehle.io
   There is no native
   implementation
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7. Tommy Mühle | tommy-muehle.io 7
   https:/
   /wiki.php.net/rfc/enum
   

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8. Tommy Mühle | tommy-muehle.io 8
   https:/
   /docs.hhvm.com/hack/enums/introduction
   

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9. Tommy Mühle | tommy-muehle.io
   Without enum
   classes
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10. Tommy Mühle | tommy-muehle.io 10
    Avoid global constants
    // app.php
    const STATE_ACTIVE = 'active';
    const STATE_COMPLETED = 'completed';
    $app = new Application();
    $app->setState(STATE_ACTIVE);
    // ...
    return $app->run();
    

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11. Tommy Mühle | tommy-muehle.io 11
    class StateHandler
    {
    const STATE_ACTIVE = 'active';
    const STATE_CANCELED = 'canceled';
    public function handle($state)
    {
    if ($state !== self::STATE_ACTIVE) {
    // ...
    }
    // ...
    }
    }
    Avoid class constants
    

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12. Tommy Mühle | tommy-muehle.io
    With enum
    classes
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13. Tommy Mühle | tommy-muehle.io 13
    final class Color
    {
    const __DEFAULT = 'black';
    const RED = 'red';
    private $value;
    public function __construct(string $color = null)
    {
    $this->value = $color ?? self::__DEFAULT;
    }
    public function __toString()
    {
    return $this->value;
    }
    }
    

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14. Tommy Mühle | tommy-muehle.io
    Advantages
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15. Tommy Mühle | tommy-muehle.io
    You can get a list of
    all the values
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16. Tommy Mühle | tommy-muehle.io 16
    final class Color
    {
    // ...
    public function __construct(string $color = null)
    {
    $value = $color ?? self::__DEFAULT;
    if (!in_array($value, $this->all(), true)) {
    // ...
    }
    $this->value = $value;
    }
    public function all() : array
    {
    return (new \ReflectionClass(static::class))

    ->getConstants();
    }
    // ...
    }
    

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17. Tommy Mühle | tommy-muehle.io
    You can
    type-hint
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18. Tommy Mühle | tommy-muehle.io 18
    class Article
    {
    private $color;
    public function colorize(Color $color)
    {
    // ...
    }
    }
    

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19. Tommy Mühle | tommy-muehle.io
    You can enrich your
    classes with methods.
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20. Tommy Mühle | tommy-muehle.io 20
    final class Color
    {
    // ...
    protected $value;
    // ...
    public function value()
    {
    return $this->value;
    }
    public function equals(Color $color)
    {
    // or any other business condition
    return $this->value === $color->value();
    }
    }
    

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21. Tommy Mühle | tommy-muehle.io 21
    final class Color
    {
    // ...
    protected $value;
    // ...
    public static function fromHex(string $hex)
    {
    // do something with $hex and get $color
    return new self($color);
    }
    public function format()
    {
    return 'My special color format';
    }
    }
    

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22. Tommy Mühle | tommy-muehle.io
    You can extend
    this classes
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23. Tommy Mühle | tommy-muehle.io 23
    // if class Color are not final
    final class SpecialColor extends Color
    {
    // add further values, enrich methods, etc.
    }
    

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24. Tommy Mühle | tommy-muehle.io
    Before
    you start
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25. Tommy Mühle | tommy-muehle.io 25
    https:/
    /packagist.org/search/?q=enum
    

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26. Tommy Mühle | tommy-muehle.io
    Summary
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27. Questions?
    

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28. Thank you!
    Slides
    http:/
    /bit.ly/2isVOvl
    Images
    https:/
    /pixabay.com/
    @tommy_muehle
    

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