rfc:enum_allow_static_properties

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rfc:enum_allow_static_properties [2021/05/18 00:42] – tandrerfc:enum_allow_static_properties [2021/06/15 13:49] – tandre
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   * Date: 2021-05-17   * Date: 2021-05-17
   * Author: Tyson Andre, <tandre@php.net>   * Author: Tyson Andre, <tandre@php.net>
-  * Status: Under Discussion+  * Status: Voting
   * Implementation: https://github.com/php/php-src/pull/6997   * Implementation: https://github.com/php/php-src/pull/6997
   * First Published at: http://wiki.php.net/rfc/enum_allow_static_properties   * First Published at: http://wiki.php.net/rfc/enum_allow_static_properties
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   - [[https://en.wikipedia.org/wiki/Memoization|Memoization]] of expensive operations with no side effects (reading and parsing a large file from disk, cpu-intensive operations, service/db calls)   - [[https://en.wikipedia.org/wiki/Memoization|Memoization]] of expensive operations with no side effects (reading and parsing a large file from disk, cpu-intensive operations, service/db calls)
   - Keeping track of which enum case reflects the current state of a state machine or system   - Keeping track of which enum case reflects the current state of a state machine or system
 +
 +E.g. for [[https://en.wikipedia.org/wiki/Memoization|Memoization]], it may be useful to keep the result of expensive operations with no side effects in a static properties in the same module. Typically, php static properties are used where many other languages may have module functions and state in a file separate from a class definition (e.g. due to autoloading and coding standards requiring one class per file).
 +
 +<code php>
 +// https://en.wikipedia.org/wiki/Sprite_(computer_graphics)
 +enum Sprite {
 +    case FROG;
 +    case LOG;
 +    case GRASS;
 +    case WATER;
 +    // etc.
 +    
 +    /** @var array<string, MyModule\ImageData> */
 +    private static array $cache = [];
 +    
 +    public static function getImageData(SpriteArt $value): MyModule\ImageData {
 +        $key = $value->name;
 +        if (!isset(self::$cache[$key])) {
 +            self::$cache[$key] = self::loadImageData($value);
 +        }
 +        return self::$cache[$key];
 +    }
 +    
 +    // Called when is no longer used, the color scheme changed, etc.
 +    public static function clearImageData(SpriteArt $value): void {
 +        self::$cache = [];
 +    }
 +    
 +    // Slow operation: Read image data from disk and decode image data.
 +    public static function loadImageData(): void {
 +        // ...
 +    }
 +}
 +</code>
  
 For example, one way to represent fetching the current environment (of a known enumeration of environments) would be a static method on the environment enum itself. The environment instance is immutable, but the environment being loaded depends on a file. For example, one way to represent fetching the current environment (of a known enumeration of environments) would be a static method on the environment enum itself. The environment instance is immutable, but the environment being loaded depends on a file.
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 ===== Unaffected PHP Functionality ===== ===== Unaffected PHP Functionality =====
 Instance properties continue to be forbidden on enums. Instance properties continue to be forbidden on enums.
 +
 +PHP enums were already able to have instance and static methods.
  
 ===== Discussion ===== ===== Discussion =====
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-===== Proposed Voting Choices ===== +===== Vote ===== 
-Yes/No, requiring a 2/3 majority+This is a Yes/No vote, requiring a 2/3 majority. 
 + 
 +Voting started on June 1, 2021 and ends on June 15, 2021
  
 +<doodle title="Allow static properties in enums" auth="tandre" voteType="single" closed="true">
 +   * Yes
 +   * No
 +</doodle>
 ===== References ===== ===== References =====
 https://externals.io/message/112626#113037 brought up the same suggestion. https://externals.io/message/112626#113037 brought up the same suggestion.
  
 [[enumerations|enums RFC]] [[enumerations|enums RFC]]
rfc/enum_allow_static_properties.txt · Last modified: 2021/06/16 03:29 by tandre

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