How to Decouple IoC Framework Implementation

Question

I've been learning IoC, Dependency Injection etc. and enjoying the process. The benefits of decoupling and programming to interfaces are, to me, a no-brainer.

However, I really don't like binding myself to a specific framework like Unity or Autofac or Windsor - because I'm still learning and haven't yet decided which is best for my purposes.

So, how can I wrap around something like Unity so I could easily swap in Windsor at a later date? (or whatever). And don't you dare say use another one to inject the first one ;)

Thanks!

R.

P.s. I tagged Unity as that's my current personal preference (I just lurve Entlib).

Answer 1

You can certainly try making an abstraction from the container by declaring an IContainer with say Resolve and Register. I did that a couple of times. Then you would go ahead and implement a Container : IContainer and encapsulate an actual IoC container with your abstraction. I tried that with Unity and Castle Windsor.

But hey, soon I realised that this was really an over-engineering. I then understood that I tried to abstract from abstraction, yet to build another abstraction. This could be fine to learn the concept, but it was a real pain in the neck in a real project. I would highly recommend against an abstraction from IoC container. If you correctly use DI principle it will be fairly easy to change your container anyways.

The code looks overcomplicated, like

//I did this mess with Service Locator
var t = ContainerService.Instance.Resolve<IMyType>();
//others could go further with same Service Locator
var t = IoCFactory.Instance.CurrentContainer.Resolve<IMyType>();

//better way, use --> IoC and DI <--
//when a program starts, or a new instance of the context created
var t = Container.Resolve<IMyType>() //this lives at the bottom of the stack
//and then you just pass IMyType to the constructor of other types    
//you don't need to call Resolve again in the logical cycle

See this post by Ayende.

Yes, they abstracted the Inversion of Control Container. I think that if you need to do that, it is pretty clear that you don’t really get what IoC is all about.