> On Dec 31, 2020, at 12:15 PM, Larry Garfield <la...@garfieldtech.com> wrote:
>
> On Thu, Dec 31, 2020, at 6:53 AM, Rowan Tommins wrote:
>> On 30/12/2020 21:24, Aleksander Machniak wrote:
>>> My argument is that, from an end-user perspective, I don't really see
>>> why Unit and Scalar enums have to have different "API" at this point.
>>> I'm talking about ":string"/":int" in the enum definiton as well as
>>> ->value and ->from().
>>
>>
>> My personal opinion is that for many enums, explicitly not having a
>> scalar representation is a good thing.
>>
>> This is basically similar to my opinion of __toString() etc: if you have
>> *multiple* ways to convert something to/from a scalar, blessing one of
>> them as "default" is arbitrary and confusing.
>>
>> For example:
>>
>> enum BookingStatus {
>> case PENDING;
>> case CONFIRMED;
>> case CANCELLED;
>>
>> public function getId() {
>> return match($this) {
>> self::PENDING => 1,
>> self::CONFIRMED => 2,
>> self::CANCELLED => 3,
>> };
>> }
>> public function getCode() {
>> return match($this) {
>> self::PENDING => 'PEN',
>> self::CONFIRMED => 'CON',
>> self::CANCELLED => 'CAN',
>> };
>> }
>> public function getEnglishDescription() {
>> return match($this) {
>> self::PENDING => 'Pending Payment',
>> self::CONFIRMED => 'Confirmed',
>> self::CANCELLED => 'Cancelled',
>> };
>> }
>> }
>
> That is similar to our reasoning. It creates a foot-gun situation where
> someone could get in the habit of assuming that an enum always has a
> *reasonable* and *logical* and thus *reliable* string equivalent, when not
> all enums will have string equivalents that it's reasonable and logical to
> use. So, one less foot gun.
However, avoiding one foot-gun does not always mean that you avoid all
foot-guns.
For example, when you need to create a large number of string enums where the
name and the symbol are the same, it would be very easy to have a typo in one
but not the other, especially as a result of copy and paste editing.
So in my perfect world this:
enum BookingStatus {
case PENDING;
case CONFIRMED;
case CANCELLED;
}
Would be equivalent to:
enum BookingStatus {
case PENDING = "PENDING";
case CONFIRMED = "CONFIRMED";
case CANCELLED = "CANCELLED";
}
#fwiw
>
> Also, one of the extensions planned, as noted, is ADTs/tagged unions. Those
> could not have a primitive equivalent, since they're not singletons. Keeping
> UnitEnum and ScalarEnum separate allows us to later add TaggedEnum (or
> similar) that also extends UnitEnum, but not ScalarEnum.
>
> --Larry Garfield
>
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