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
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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User Contributed Notes 2 notes
theking2 at king dot ma ¶
2 years ago
ratsimbasitraka at gmail dot com ¶
1 year ago
enum Priority {
case Left;
case Right;
}
// Does not work as default parameter
public function selectPriorities(array $priorities = Priority::cases()) {
Priority::cases() // works here
}
