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PHP 7.1+ 的枚举库

当需要只允许接受有限集合中的一个值时，枚举类型非常有用。它还有助于逻辑上将它们分组在同一个地方。

其接口主要基于java.lang.Enum，但实现为其添加了一些额外的魔法。

基本用法

namespace My\App;


/**
 * List of all available days.
 *
 * @method static Day MONDAY()
 * @method static Day TUESDAY()
 * @method static Day WEDNESDAY()
 * @method static Day THURSDAY()
 * @method static Day FRIDAY()
 * @method static Day SATURDAY()
 * @method static Day SUNDAY()
 */
class Day extends \Donatorsky\Enum\Enum
{

    // Make available values private/protected if You want to force using getters
    private const MONDAY    = 1;
    private const TUESDAY   = 2;
    private const WEDNESDAY = 3;
    private const THURSDAY  = 4;
    private const FRIDAY    = 5;
    private const SATURDAY  = 6;
    private const SUNDAY    = 7;

    /**
     * @var int
     */
    protected $value;


    /**
     * Day constructor.
     *
     * @param int $value
     */
    protected function __construct(int $value)
    {
        $this->value = $value;
    }


    /**
     * @return int
     */
    public function getValue(): int
    {
        return $this->value;
    }
}

// Somewhere deep in code...

function getDeveloperState(Day $day): string
{
    switch ($day) {
        case Day::MONDAY():
            return 'Get redy to work';
        break;

        case Day::TUESDAY():
        case Day::WEDNESDAY():
        case Day::THURSDAY():
            return 'Work hard';
        break;

        case Day::FRIDAY():
            return 'Save all work';
        break;

        case Day::SATURDAY():
        case Day::SUNDAY():
            return 'Save all work';
        break;

        // If You add new constants
        default:
            return 'Where am I?!';
        break;
    }
}

// Let's see what to do on friday...
echo getDeveloperState(Day::FRIDAY()) . PHP_EOL;

// Or today
/**
 * In fact fromValue() will always return object of type that was called on
 * @var Day $today
 */
$today = Day::fromValue(date('N'), false);

echo getDeveloperState($today) . PHP_EOL;

// Get constant name of current day
echo $today->name() . PHP_EOL;

// Or check if it is specified day
echo 'Is monday today? ' . ($today->is('MONDAY') ? 'Yes' : 'No') . PHP_EOL;

// Or check it in other way
echo 'Is monday today? ' . ($today->equals(Day::MONDAY()) ? 'Yes' : 'No') . PHP_EOL;

// Tell me who am I...
// Note: Also __toString() uses hashCode(), so "$today" will work unless hashcode() is overwritten
echo $today->hashCode() . PHP_EOL;

// Call (optional) getter of value
echo 'Value of current day is ' . $today->getValue();

// Let's see if there is a day named...
echo 'Is NON_EXISTING_DAY real? ' . (Day::has('NON_EXISTING_DAY') ? 'Yes' : 'No') . PHP_EOL;

// So which days are true?
echo 'Please, choose one of following days: ' . implode(', ', Day::keys()) . PHP_EOL;

// Ok, last question
// Note: valueOf() returns object of Day class
echo 'What is the value of WEDNESDAY? ' . Day::valueOf(Day::class, 'WEDNESDAY')->getValue();

与其他实现的主要区别在于，它允许常量具有复杂值

namespace Donatorsky\Enum\Tests;

use Donatorsky\Enum\Enum;


/**
 * Class Rectangle
 *
 * @method static Rectangle SMALL()
 * @method static Rectangle MEDIUM()
 * @method static Rectangle LARGE()
 *
 * @package Donatorsky\Enum\Tests
 */
class Rectangle extends Enum
{

    public const SMALL  = [ 2,  3, 'RED'];
    public const MEDIUM = [ 5,  8, 'GREEN'];
    public const LARGE  = [13, 21, 'BLUE'];

    /**
     * @var float
     */
    protected $width;

    /**
     * @var float
     */
    protected $height;

    /**
     * @var float
     */
    protected $area;

    /**
     * @var Color
     */
    protected $color;


    /**
     * Rectangle constructor.
     *
     * @param float  $width
     * @param float  $height
     * @param string $color
     */
    protected function __construct(float $width, float $height, string $color)
    {
        $this->width = $width;
        $this->height = $height;
        $this->area = $width * $height;
        $this->color = Color::$color();
    }


    /**
     * @return float
     */
    public function getWidth(): float
    {
        return $this->width;
    }


    /**
     * @return float
     */
    public function getHeight(): float
    {
        return $this->height;
    }


    /**
     * @return Color
     */
    public function getColor(): Color
    {
        return $this->color;
    }


    /**
     * @return float
     */
    public function getArea(): float
    {
        return $this->area;
    }
}