> Am 3.6.2016 um 18:49 schrieb Larry Garfield <la...@garfieldtech.com>:
>
> On 06/03/2016 10:16 AM, Jordi Boggiano wrote:
>> On 03/06/2016 15:58, Thomas Bley wrote:
>>> To me type declarations help to make my code easier and more consistent.
>>> Having multiple scalar types for a single function parameter is against
>>> this goal since I need extra logic to handle this.
>>>
>>> e.g. function foo(string | int | bool $bar) {} makes no sense in weak mode
>>> since string can already handle int, bool, float, etc.
>>>
>>> having different behavior between
>>> foo("42"); function foo(string $b) {echo gettype($b);} // string
>>> and
>>> foo("42"); function foo(string | int $b) {echo gettype($b);} // integer
>>> also makes no sense to me.
>>>
>>> Things like string|array are useful (e.g. str_replace) since we can cast
>>> the string easily to array and calling a string parameter with an array
>>> would give a fatal error.
>>
>> That is a useful case, and don't forget also return values, e.g. all the
>> XX|false-kind of return types it's also nice to have.
>>
>> I don't think for function arguments it's massively useful and I doubt it'll
>> get put everywhere, but it's nice to be able to express this when you have
>> to.
>>
>> Cheers
>
> For parameters, I really don't think | is going to be the common use case.
> (It should still be rational, but I don't expect to see it day to day.)
> InterfaceA & InterfaceB Is the more useful use case for parameters. | is, as
> noted, likely more useful on returns. (even though I would discourage their
> use in most cases for reasons I won't go into here).
>
> --Larry Garfield
It won’t and it should not be *common*. But there are legit uses cases:
https://github.com/amphp/aerys/blob/2a4d626fb1b8b8ac9d91711085c04eaabdec7768/lib/Host.php#L87
<https://github.com/amphp/aerys/blob/2a4d626fb1b8b8ac9d91711085c04eaabdec7768/lib/Host.php#L87>
This concrete example shows that a class may implement multiple concrete
interfaces which all get the same/similar behavior locally. [And somewhere else
the code checks for each element in the array what classes it implements and
marks them appropriately.]
Sure, you could have ->addMiddleware($foo)->addRequest($foo) … or just a single
->add($foo). It’s maybe not the most pure API, but the most practical one.
But I agree, I myself would discourage usage of union types in most cases too;
but there *are* legitimate cases which shall be also properly typable. Thus we
need it.
Bob
