Re: RFC: Functional Interfaces

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. Regards, -- Rowan Collins [IMSoP]