Re: Closures and type hinting

On Fri, Oct 12, 2012 at 10:58 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 $onFound); > } > > Now if you pass a closure to the scan method which doesn't follow the > signature of the __invoke method, the engine should throw an error. > > What do you think? Please also don't forget that PHP doesn't have strict function signatures. E.g. you can write function($foo) { echo $foo; } but you could also write function() { $foo = func_get_arg(0); echo $foo; } So I'm not sure just how much sense function signature checking makes in PHP ;) Nikita