PHP: Hypertext Preprocessor

枚举值清单

无论是纯粹枚举还是回退枚举，都实现了一个叫 UnitEnum 的内部接口。 UnitEnum 包含了一个静态方法： cases()。按照声明中的顺序，cases() 返回了打包的 array，包含全部定义的条目。

<?php

Suit::cases();
// 产生： [Suit::Hearts, Suit::Diamonds, Suit::Clubs, Suit::Spades]
?>

为 Enum 手动定义 cases() 方法会导致 fatal 错误。

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theking2 at king dot ma ¶

2 years ago

As ::cases() creates a Iteratable it is possible to use it in a foreach loop. In combination with value backed enum this can result in very compact and very readable code:

<?php
/** Content Security Policy directives */
enum CspDirective: String {
  case Default = "default-src";
  case Image = "img-src";
  case Font = "font-src";
  case Script = "script-src";
  case Style = "style-src";
}

/** list all CSP directives */
foreach( CspSource::cases() as $directive ) {
  echo $directive-> value . PHP_EOL;
}
?>
Which results in:
default-src
img-src
font-src
script-src
style-src

down

anhaia dot gabriel at gmail dot com ¶

2 months ago

If you want to get all the values of the Enum in a list of `string`, you might do something like this:

<?php

enum MyEnum: string
{
    case OPTION_A = 'option_a';
    case OPTION_B = 'option_b';
    case OPTION_C = 'option_c';

    public static function values(): array
    {
        return array_map(fn ($case) => $case->value, self::cases());
    }
}

?>