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。
＋添加备注
用户贡献的备注 2 notes
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 $directive-> value . PHP_EOL;
}
?>
Which results in:
default-src
img-src
font-src
script-src
style-src
anhaia dot gabriel at gmail dot com ¶
6 months ago
If you want to get all the values of the Enum in a list of `string`, you might do something like this:
<?php
enum MyEnum: string
{
case OPTION_A = 'option_a';
case OPTION_B = 'option_b';
case OPTION_C = 'option_c';
public static function values(): array
{
return array_map(fn ($case) => $case->value, self::cases());
}
}
?>备份地址：http://www.lvesu.com/blog/php/language.enumerations.listing.php