Service Autowiring

Hey ahmedbhs
I'll answer your questions in the same order:

1) First of all in a Controller's action you don't inject a Response object, you're supposed to return one. You inject the Request object so you can get access to all the parameters coming from it (like $_POST, $_GET, $_SERVER)

2) The "Request" object as I mentioned above contains all those global parameter but the "RequestStack" is a collection of requests because you can have many request coming from a single request. There are two types of requests, Master and Sub request, probably if you give it a check to the "Kernel" class you will understand it better

3) I usually inject my services as method arguments, but if there is a service that I'll use on ALL controller's action, then, I would inject it on the constructor. The reason of injecting it on the method is because I don't want to instantiate objects that I won't use in the given request.

I believe this last answer, answers all your related questions about injecting services in the constructor or as a method argument

Cheers!

Hey James!

Yea, great conversation question. First, the reason auto-wiring isn't available for method calls is simply that you (other than the controller) call your methods directly - there's no information about method arguments in the service container itself. The service container only cares about instantiating your objects.

The only time that Symfony calls your method automatically is in the case of the controller. And in this special case, you can take a different route to accomplish what you need. Specifically, you could register a listener (on kernel.controller), read the type-hints from your arguments, fetch services out for those type-hinted classes, and inject them as arguments. This is a non-trivial task of course, and you probably won't want to loop over *every* service to find which match your type-hint. Instead, you'll probably need some configuration that says "type hint Foo\Bar goes to service foo_bar". For people defining controllers as services, it's actually a pretty rad idea... and if done well, could maybe be introduced into SensioFWExtraBundle.

Anyways, you can kind of get an idea on how to make something like this from SensioFrameworkExtraBundle - it's ParamConverter does exactly this (i.e. it looks at the type-hint of arguments and uses that to automatically query for an entity of that type).

Let me know how it goes :)

Hey Ryan,

There's already an injector I use called Auryn that provides a couple of methods that provide similar functionality. It has make() which creates an object and its dependencies recursively, and execute() which, given a callable, object + method etc, uses the same introspective logic to recursively instantiate dependencies of the given object's method. I've been using this in a microframework for a while for my controllers and, for me, it's really the only thing that's missing for jumping over to the full Symfomy framework.

I've done some research into the kernel and, short of rewriting the whole thing, it doesn't look like I can override the controller calling. As awesome and modular as Symfony and its Kernel is, that call_user_func() for the controller + method combo is in a private method! Of all the things! If only that call could be placed in another protected method so it can be overriden, perhaps this is something we could collaborate on if it still piques your interest?

Relevant research in my SO question: http://stackoverflow.com/qu...

I'll take a look at the framework bundle and ParamConverter. As developers tend to start working on a new feature in the controller layer, the ability to get working with it quickly in controller actions (although as you said, being an edge case, is still a common one) would be awesome.

Thanks for the quick and in depth response! I enjoy following how KNP is doing and looking forward to checking out the Symfony 3 tuts!

Hey James!

Yea, I'm definitely interested in this :). So, the stuff in Kernel is private on purpose (which I'm sure you suspected already). Symfony uses call_use_func_array(), but you can hook into both the functionality that determines the controller callable and the functionality that determines that callable's arguments. So, if Auryn is able to give you back the arguments it determines, but *not* actually call the callable, then you'll be able to hook in without any issues. You would do that either by overriding the ControllerResolver or (preferably, cause it's easier to hook into existing projects) by using my previous recommendation. Basically, if you register a listener on kernel.controller, then whatever "stuff" you add to $request->attributes becomes available as a controller arg. For example, if I say `$request->attributes->set('router', $myRouter)`, then this $myRouter will be passed to a $router argument of my controller method (if it has one). That matching is done by name, but you could have originally figured out the object to pass to the $router argument by using Auryn to "guess" based on the type-hint etc.

So, as I said, non-trivial - but all the hook points should be there :).

Cheers!

Hey Matias C.

That's a good question. Since you are not in Symfony 3.3, you cannot take advantage of auto-registration, so, what you will have to do is register a new service for each class that you want to specifically inject/use, and manually wire up the service what is going to use it.

Cheers!

Actually my problem was injecting the event_dispatcher. In Symfony 3.3 and up, I had to use the interface, otherwise, I had to use a specific dispatcher. I could have wired the service manually, but instead I removed the EventDispatcher from the constructor and used the "calls" with "@event_dispatcher". This solved the issue, hope that this helps.

Hey Matias C.

I'm glad to hear that you could fix your problem, but if you really want to inject it, you could create an alias for the "EventDispatcherInterface" and point it to the specific dispatcher that you want to use for all general cases
Maybe this videos may help you understanding how to handle problems like this
https://knpuniversity.com/s...
https://knpuniversity.com/s...

Cheers!

Ok, I'll give it a try, thanks.

Hey Waleed,

I think it's impossible out of the box since you need to use factory, i.e. call getRepository() method like:

services:
    app_blog_repository:
        class: AppBundle\Repository\BlogRepository
        factory: ['@doctrine.orm.default_entity_manager', getRepository]
        arguments:
            - AppBundle\Entity\Blog

And pass an entity name as a string as the first argument to the method. But the string could not be resolved with autowiring, you have to specify it manually.

Cheers!

Thank you! new factory config looks like

services:
    app_blog_repository:
        class: AppBundle\Repository\BlogRepository
        factory: 'doctrine.orm.default_entity_manager:getRepository'
        arguments:
            - AppBundle\Entity\Blog

Ah, the new factory syntax, nice! Thanks for sharing it

Hey Mike!

Maybe they just don't like magic, or they have lived some of the few edge cases about autowiring

Cheers!