Re: Closures and type hinting

On Oct 12, 2012 10:59 AM, "Christian Kaps" <christian.kaps@mohiva.com> wrote: > > At the moment it isn't possible to restrict/define the arguments for a closure which is defined as parameter for a method. Please look at this small example. > > interface Broker { > > public function scan(Request $request, Closure $onFound); > } > > An implementation of the interface could be as follows: > > class BrokerImpl implements Broker { > > /** > * @var Service > */ > private $service = null; > > public function scan(Request $request, Closure $onFound) { > > if ($request->contains('some value')) { > $onFound($this->service); > } > } > } > > The problem is that I can pass every closure to the scan method. > > $broker = new BrokerImpl(); > $broker->scan($request, function() { /* do something */ }); > > Sometimes I would like to restrict the closure passed to this method. So that only closures of a certain type which has an argument "Service $service" could be passed to this method. > > $broker = new BrokerImpl(); > $broker->scan($request, function(Service $service) { /* do something */ }); > > Would it not be possible to extend the Closure class and then define an abstract method signature for the __invoke method. > > class OnFoundClosure extends Closure { > > public abstract function __invoke(Service $service); > } > > And then you can define the interface as follows: > interface Broker { > > public function scan(Request $request, OnFoundClosure $onFound); > } > > Now if you pass a closure to the scan method which doesn't follow the signature of the __invoke method, the engine should throw an error. > > What do you think? > > -- > PHP Internals - PHP Runtime Development Mailing List > To unsubscribe, visit: http://www.php.net/unsub.php > Honestly, I would suggest using a class directly if you want that kind of type control. Closures are meant to be a conscience, not the end all be all implementation. I understand what you are looking for. But to me, unless we implemented function pointers (typeable callbacks), I can't see the generalized use case. At least that isn't already solvable using classes, interfaces and polymorphism... Anthony