Hi Larry,
Thank you for the comment.
> It seems like what you're describing here is more user-customizable
> autoboxing than anything to do with union types.
Your first statement ("user-customizable autoboxing") is probably fair to say.
OTOH, rather than say "anything to do with union type" I would instead say
"where union-types is an excellent use-case for auto-boxing."
> For that, it seems like you'd want more of a fromString() method (magic or
> interface):
That would certainly work.
But unfortunately that requires the class developer to be forward-thinking
enough to implement methods required for all the use-cases of their class
users, and I think it is unlikely we can depend on that case for most classes
in the wild.
What I'd rather see is a solution that gives the user of the class more control
and a well-known/consistent programming model (e.g. ->toGuid().)
> Whether or not something like that is wise I don't know, but it seems like it
> would resolve the use case you describe better than fiddling with union
> types. Or am I totally misunderstanding you as well? :-)
I made the proposal because I felt that auto-boxing was the best solutions for
the union-types use-case. So if renaming the proposal to "user-customizable
autoboxing" is more preferred by others I'd see that to be fine, assuming it
was implemented in a manner that allowed for adding the use-case of union
types. :-)
-Mike
P.S. I am not seeing much traction from this proposal so even though we discuss
the nuances it seems likely it won't matter beyond this discussion.
> On Sep 11, 2019, at 6:07 AM, Larry Garfield <[email protected]> wrote:
>
> On Sun, Sep 8, 2019, at 2:11 PM, Mike Schinkel wrote:
>> Hi Stephen,
>>
>> Thanks again.
>>
>>> So let me start out by clarifying that what *I* was suggesting with unions
>>> is quite a different concept than you’re talking about.
>>
>> I did not realize you were proposing a different solution, too. Sorry I
>> missed that.
>>
>>> yes, I’m aware there’s potential ambiguous cases - what if the destination
>>> accepts `string|int` and the object supports both interfaces?
>>
>>
>> Precisely. And the goal of my proposal was in part to eliminate that
>> ambiguity.
>>
>>> Ok - the example given makes “sense” with the understanding that it’s
>>> alternative ‘short’ syntax - but that makes it yet another step further
>>> from ‘intuitive’ to me, compared with current type hints, and the extension
>>> to allow unions Nikita introduced -
>>
>> Acknowledged.
>>
>>> and if Im not mistaken it makes it incompatible too (i.e. you can’t have
>>> the behaviour Nikita’s RFC describes and what you describe with the
>>> ‘anonymous unions’ - they’re too very different approaches using the same
>>> syntax.
>>
>> I do not see how they are incompatible except for the details mine
>> changes, but maybe that is moot at this point?
>>
>>> I think the intuitiveness factor is easier to explain if you consider the
>>> case of the Number example - plenty of things will work exactly as you
>>> expect if you use either an int or a float. But then with your proposal
>>> suddenly you don’t have a scalar variable any more - yes I know you can
>>> call `value()` - part of the point of type hints is to reduce boilerplate
>>> with type checking arguments within the function body - and now you have to
>>> call a method to get a usable value anyway?
>>
>> I do not see any technical reason why mine would not be able to behave
>> the same using the magic methods you were proposing such as
>> __toString() and for other scalar types — since fundamentally the
>> proposed union type would be a class anyway. When used that way it
>> would nullify the benefit of the explicit typing, but if that is what
>> the developer wanted who was using then why not?
>>
>> In that context it would be almost the same as just passing in a scalar.
>>
>>> The GUID example still confuses me in terms of how your example ‘helps’. If
>>> $guid->getGuid returns null (signifying it’s a string?) presumably I still
>>> want to do something with that string - otherwise I wouldn’t have accepted
>>> it as a valid type - at which point I might as well just do a `instanceof`
>>> or `is_string` call - but now I have to check if the value I was given is
>>> null, even if I didn’t specify the parameter as being nullable?
>>
>> It does not help that way. The main help is with $guid->type() which
>> can be used in a switch. It's just cleaner code, though I can
>> appreciate that some might see this as not really a benefit:
>>
>> function processGuid(string|Guid $guid) {
>> switch( $guid->type()) {
>> case 'Guid':
>> $guid->toGuid()->doSomething();
>> break;
>> case 'string':
>> $g = new Guid($guid->toString());
>> $g-> doSomething();
>> break;
>> }
>> }
>>
>> The other benefit is that it becomes a first-class concern that can be
>> extended when named union classes are used so I could implement this
>> inside the union class and use it in many functions like this, if I
>> wanted, rather than have to use type checking boilerplate in Every.
>> Single. Function:
>>
>> class GuidUnion {
>> types string|Guid
>> public function doSomething() {
>> switch( $this->type()) {
>> case 'Guid':
>> $this->toGuid()->doSomething();
>> break;
>> case 'string':
>> $g = new Guid($this->toString());
>> $g-> doSomething();
>> break;
>> }
>> }
>> }
>>
>> /**
>> * HERE is where you start seeing a real benefit...
>> */
>> function processGuid1(GuidUnion $guid) {
>> $guid->doSomething();
>> }
>> function processGuid2(GuidUnion $guid) {
>> $guid->doSomething();
>> }
>> function processGuid3(GuidUnion $guid) {
>> $guid->doSomething();
>> }
>>
>>
>>> I think (or I hope so at least) we’re at least both clear what the other is
>>> talking about now.
>>
>> Hopefully, with that last point clarified, yes.
>>
>> Thanks again.
>>
>> -Mike
>
> It seems like what you're describing here is more user-customizable
> autoboxing than anything to do with union types. Viz, since a Guid has a
> natural and round-trippable string representation, you want to be able to ask
> for a Guid, be given a string, and then work with it as a Guid either way.
>
> For that, it seems like you'd want more of a fromString() method (magic or
> interface):
>
> class Guid implements FromStringInterface {
>
> public static function fromString(string $s) {
> if (is_valid_guid($s)) {
> return new static($s);
> }
> throw new \TypeError();
> }
> }
>
> function needGuid(Guid $g) {
> $g->doGuidThings();
> }
>
>
> needGuid('a9d05a5f-e643-441e-8784-cfd613072072');
>
> Whether or not something like that is wise I don't know, but it seems like it
> would resolve the use case you describe better than fiddling with union
> types. Or am I totally misunderstanding you as well? :-)
>
> --Larry Garfield
>
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