Wednesday, 27 July 2016

PHP / Silex / Dependency injection: should I use a reference to a method?

This is another example of where I want to put a question out there, but it needs more space that Twitter will allow. I guess I'll put it on Stack Overflow too.

We use Silex and Pimple's DI container. Generally in our service providers we expose references to objects, eg:

$app['service.something'] = $app->share(function ($app) {
    return new SomethingService();

Then usage of that is predictable:

$result = $app['service.something']::someMethod(1, 2, 3);

But here's the thing. As with the case above, the method is actually a static one. So it seems "odd" to be calling it on an instance of the SomethingService, rather than on the class. As coincidence would have it, this is the only public method in SomethingService too.

So we've done this sort of thing in our service provider:

$app['something'] = $app->protect(function ($arg1, $arg2, $etc) {
    return SomeClass::someMethod($arg1, $arg2, $etc);


$result = $app['something'](1, 2, 3);

Now this works OK, but I have a coupla hesitations:
  • the name $app['something'] is a bit noun-y. As it's a method it ought to be verb-y IMO, eg: $app['doTheThing']. I guess that's small fish.
  • I'm just not sure if it's particularly "semantic" to be exposing just methods like that. All usage of Pimple I've seen has been to expose dependent objects.
I think we'll run with what we've got, but I kinda want to get more thoughts on if this is the right approach. And if so (or if not) why not. There might be some gotchas here I'm not thinking of, or something.