PHP: Hypertext Preprocessor

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、静态方法和常量。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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wervin at mail dot com ¶

1 year ago

One good example of a trait, would be to give a lot of enums a method to retrieve their cases, values or both.<?phptrait 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:<?phpvar_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']