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Date: Tue, 19 Apr 2016 17:48:48 +0300
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Subject: Re: [PHP-DEV] RFC: Functional Interfaces
From: dmitry@zend.com (Dmitry Stogov)



On 04/19/2016 05:30 PM, Rowan Collins wrote:
> Dmitry Stogov wrote on 19/04/2016 15:12:
>> I prefer intuitive concepts, that I may use without rereading manual 
>> again and again.
>> For this one, I even can't imagine a natural (not over-designed) use 
>> case. 
>
> The use case that came to my mind is kind of the other way around from 
> "syntax sugar for anonymous classes" - providing a contract for what a 
> callback should look like. In essence, it's an alternative to 
> specifying closure type with a generic-like syntax, as proposed at 
> https://wiki.php.net/rfc/callable-types
>
> Say you currently have this:
>
> public function registerCallback(callable $callback) { ... }
>
> You could instead specify what the callback needs to accept and return:
>
> interface EventCallbackInterface {
>     public function __invoke(Event $event): boolean;
> }
> public function registerCallback(EventCallbackInterface $callback) { 
> ... }
>
> Using __invoke as the method name may or may not be a good idea, but 
> it interestingly means I don't need to change the code that runs the 
> callback, I can just use $callback($some_event); Then if someone wants 
> to use a complex object, they can; and if they just want to use a 
> closure, it has to meet the contract.

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?

Thanks. Dmitry.
>
>
> Regards,