Re: RFC: Functional Interfaces

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