CascadiaPHP 2024

Trait

枚举也能使用 trait,行为和 class 一样。 留意在枚举中 use trait 不允许包含属性。 只能包含方法、静态方法。 包含属性的 trait 会导致 fatal 错误。

<?php

interface Colorful
{
public function
color(): string;
}

trait
Rectangle
{
public function
shape(): string {
return
"Rectangle";
}
}

enum
Suit implements Colorful
{
use
Rectangle;

case
Hearts;
case
Diamonds;
case
Clubs;
case
Spades;

public function
color(): string
{
return match(
$this) {
Suit::Hearts, Suit::Diamonds => 'Red',
Suit::Clubs, Suit::Spades => 'Black',
};
}
}
?>
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User Contributed Notes 1 note

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10
wervin at mail dot com
5 months ago
One good example of a trait, would be to give a lot of enums a method to retrieve their cases, values or both.

<?php
trait EnumToArray
{
public static function
names(): array
{
return
array_column(self::cases(), 'name');

}

public static function
values(): array
{
return
array_column(self::cases(), 'value');
}

public static function
asArray(): array
{
if (empty(
self::values())) {
return
self::names();
}

if (empty(
self::names())) {
return
self::values();
}

return
array_column(self::cases(), 'value', 'name');
}
}
?>

Some example outputs:

<?php
var_export
(IpVersion::names()); // ['Ipv4', 'IPv6']
var_export(IpVersion::values()); // []
var_export(IpVersion::asArray()); // ['IPv4', 'IPv6']

var_export(Language::names()); // ['en', 'es']
var_export(Language::values()); // ['English', 'Spanish']
var_export(Language::asArray()); // ['en' => 'English', 'es' => 'Spanish']
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