Re: [IDEA] allow extending enum

On Wed, Mar 29, 2023 at 10:31 AM Rokas Šleinius <raveren@gmail..com> wrote: > > Enums were a very useful addition to PHP, however one aspect of them is neither > explicitly documented - or seemingly even talked about. > > Enums were implemented as final so they cannot be extended nor can extend > anything else. > > From a user perspective it's surprising - and actually limiting. > > USAGE EXAMPLE: > I am making an error management system: each error presented to the user > must have a unique code visible. > > ```php > class SystemError > { > public function __construct( > private string $errorText, > private ErrorCode $code > ) { > } > > public function __toString(): > { > return $this->errorText . ' ' . $this->code->toString(); > } > } > // ... > > enum ErrorCode > { > case Code_1; > case Code_2; > > public function toString(): string > { > return 'Error code:' . substr($this->name, strlen('Code_')); > } > } > ``` > > Now I want to modify it to support different modules with different > namespaces for > errors, e.g. an ApiError, simple enough: > > ```php > enum BaseErrorCode > { > // ... > } > > enum ErrorCode extends BaseErrorCode > { > case Code_1; > case Code_2; > > // ... > } > > enum ApiErrorCode extends BaseErrorCode { > // ... > function toString(): string > { > return 'Error code:API-' . substr($this->name, strlen('Code_')); > } > } > ``` > > This results in a syntax error. > > PROPOSAL: > > Enums should be able to extend other enums. > > For a complete wishlist, add: > * abstract enums; > * enums allowed to implement interfaces; > > However since I have no experience in PHP source code, I can only > provide the test suite for a possible PR this might have :( > > Do you think this is likely to get implemented? > > -- > PHP Internals - PHP Runtime Development Mailing List > To unsubscribe, visit: https://www.php.net/unsub.php > Hey Rokas, My approach has been to use an intersection type like: BackedEnum&MyCustomBehaviorInterface This works for me but it'd be interesting if something like that wouldn't work for you.