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Message-ID: <57164CE8.4090307@garfieldtech.com>
Date: Tue, 19 Apr 2016 10:21:12 -0500
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Subject: Re: [PHP-DEV] RFC: Functional Interfaces
From: larry@garfieldtech.com (Larry Garfield)

On 4/19/16 10:02 AM, Rowan Collins wrote:
> Dmitry Stogov wrote on 19/04/2016 15:48:
>> callable-type is much simpler solution for this use-case.
>> Usage of Interfaces to check function prototypes is a bit tricky, but 
>> yes, this is a possible use-case.
>> Do you like to work with framework, that use this trick for every 
>> callback? 
>
> If you don't use __invoke as the function name, you can have a single 
> class implement multiple contracts, e.g. to register for more than one 
> event type with different signatures.
>
> I guess if you had callable-types *and* union types, you could get the 
> best of both worlds:
>
> interface UserEventCallbackInterface {
>     public function handleUserEvent(UserEvent $event): boolean;
> }
> public function 
> registerCallback(EventCallbackInterface|callable(Event): boolean 
> $handler) { ... }
>
> The implementation has to be a bit fiddlier here, because you need to 
> sometimes call $handler->handleUserEvent($event) and sometimes 
> $handler($event); with a functional interface, the engine makes 
> $handler->handleUserEvent($event) work for you. The cost is that the 
> call site has to be a bit more verbose to specify the interface, 
> rather than implicitly meeting the contract.
>
> Regards,

Which is why I'm not sure I like that approach, because the place I then 
call $handler needs to have a conditional in it.  There's another RFC 
that was posted to Twitter but hasn't made it to the list yet that seems 
to solve this better:

https://wiki.php.net/rfc/callable-types

(My apologies to the authors if they aren't done with it; it's on the 
wiki so I'm assuming it's safe to mention in public.)

That allows just the callable-type syntax (which I presume is what 
you're referencing), but you can then pass an object in using 
[]-callable syntax: [$handler. 'handleUserEvent'], and then 
registerCallback() doesn't care if it was a function, method, closure, 
or whatever else. It can just () it.

-- 
--Larry Garfield