Uncle Bob stirs the pot again with "Dependency Injection Inversion"

Uncle Bob posted what was considered a rather controversial blog post, which basically pointed that just because Dependency Injection is a good thing, does not mean you cannot shoot yourself in the foot with the DI framework. He drew attention to the fact that these frameworks in their desire to be more usable have all kinds of bells and whistles, which you might just stop and think about before you jump in and start using them.

My initial reaction to this post was very positive since I always have considered the DI container something external and (potentially) replaceable. Looking from a DDD point of view (I tend to look from that one, don't I? ;) it is infrastructure which is not central to my apps, which means it should not be meshed with my core code. Hence my tweet:

I liked the point he made: you see, you can do Dependency Injection without a container. I would add, I think everyone who is doing Dependency Injection should do an exercise once in a while - write a small app without a DI container. There are two points in this exercise: one - to make sure one remembers the point Uncle Bob made, and two - to appreciate the DI containers.

Towards the end he says:

Most of the time the best kind of Dependency Injection to use, is the manual kind. Externalized dependency injection of the kind that Guice provides is appropriate for those classes that you know will be extension points for your system.

Not so sure how I feel about this one though. Most of the time I do use DI container unless the app is very very small, but unless I try I will never know, right ;)

Interestingly enough the .NET alpha-geek crowd jumped(and again and again) Uncle Bob on this one. Agreed with him for the most part and bashed him for the quote I just mentioned as well as for his example being too simplistic. I feel they are being a bit arrogant(bashing the Java tooling and all that) but they do have a point though. What do you think?

24.01.2010 | Comments [0]
Flokkur: Agile | Forritun | XP
Höfundur: Petar Shomov