Why do I need an IoC container as opposed to strai

Question

I've been using Dependency Injection (DI) for a while, injecting either in a constructor, property, or method. I've never felt a need to use an Inversion of Control (IoC) container. However, the more I read, the more pressure I feel from the community to use an IoC container.

I played with .NET containers like StructureMap, NInject, Unity, and Funq. I still fail to see how an IoC container is going to benefit / improve my code.

I'm also afraid to start using a container at work because many of my co-workers will see code which they don't understand. Many of them may be reluctant to learn new technology.

Please, convince me that I need to use an IoC container. I'm going to use these arguments when I talk to my fellow developers at work.

Answer 1

I'm a fan of declarative programming (look at how many SQL questions I answer), but the IoC containers I've looked at seem too arcane for their own good.

...or perhaps the developers of IoC containers are incapable of writing clear documentation.

...or else both are true to one degree or another.

I don't think the concept of an IoC container is bad. But the implementation has to be both powerful (that is, flexible) enough to be useful in a wide variety of applications, yet simple and easily understood.

It's probably six of one and half a dozen of the other. A real application (not a toy or demo) is bound to be complex, accounting for many corner cases and exceptions-to-the-rules. Either you encapsulate that complexity in imperative code, or else in declarative code. But you have to represent it somewhere.

Answer 2

It sounds to me like you already built your own IoC container (using the various patterns which were described by Martin Fowler) and are asking why someone else's implementation is better than yours.

So, you have a bunch of code that already works. And are wondering why you would want to replace it with someone else's implementation.

Pros for considering a third-party IoC container

• You get bugs fixed for free
• The library design may be better than yours
• People may be already familiar with the particular library
• The library may be faster than yours
• It may have some features you wish you implemented but never had time to (do you have a service locater?)

Cons

• You get bugs introduced, for free :)
• The library design may be worse than yours
• You have to learn a new API
• Too many features you will never use
• It's usually harder to debug code you did not write
• Migrating from a previous IoC container may be tedious

So, weigh your pros against your cons and make a decision.

Answer 3

IOC CONTAINER SOLVES A PROBLEM YOU MIGHT NOT HAVE BUT IT'S A NICE PROBLEM TO HAVE

http://kozmic.net/2012/10/23/ioc-container-solves-a-problem-you-might-not-have-but-its-a-nice-problem-to-have/

Answer 4

Dittos about Unity. Get too big, and you can hear the creaking in the rafters.

It never surprises me when folks start to spout off about how clean IoC code looks are the same sorts of folks who at one time spoke about how templates in C++ were the elegant way to go back in the 90's, yet nowadays will decry them as arcane. Bah !

Answer 5

I just so happen to be in the process of yanking out home grown DI code and replacing it with an IOC. I have probably removed well over 200 lines of code and replaced it with about 10. Yes, I had to do a little bit of learning on how to use the container (Winsor), but I'm an engineer working on internet technologies in the 21st century so I'm used to that. I probably spent about 20 minutes looking over the how tos. This was well worth my time.

Answer 6

I will try to find why IOC might not be good for from my perspective.

As with everything else, IOC container (or as Einstein would put it I=OC^2) is a concept you have to decide for yourself if you need it or not in your code. Recent fashion outcry about IOC is only that, fashion. Don't fall for fashion, that is first. There are myriads of concepts out there you could implement in your code. First of all, I am using dependency injection since I have started programming, and learned the term itself when it was popularized under that name. Dependency control is a very old subject and it was addressed so far in trillions of ways, depending on what was decoupling from what. Decoupling everything from everything is a nonsense. The problem with IOC container is that it tries to be as useful as Entity Framework or NHibernate. While writing an object-relational mapper is simply a must as soon as you have to couple any database with your system, IOC container is not always necessary. So when IOC container is useful:

1. When you have a situation with many dependencies you want to organize
2. When you do not care about coupling your code with third-party product
3. When your developers want to learn how to work with a new tool

1: It is not that often that you have so many dependencies in your code, or that you are aware of them early in design. Abstract thinking is useful when abstract thinking is due.

2: Coupling your code with third-party code is a HuGe problem. I was working with code that is 10+ years old and that was following at that time fancy and advanced concepts ATL, COM, COM+ and so on. There is nothing you can do with that code now. What I am saying is that an advanced concept gives an apparent advantage, yet this is cancelled on long run with the outdated advantage itself. It just had made all of it more expensive.

3: Software development is hard enough. You can extend it to unrecognizable levels if you allow some advanced concept to crop into your code. There is a problem with IOC2. Although it is decoupling dependencies, it is decoupling the logic flow as well. Imagine you have found a bug and you need to set a break to examine the situation. IOC2, as any other advanced concept, is making that more difficult. Fixing a bug within a concept is more difficult than fixing a bug in a plainer code, because when you fix a bug a concept must be obeyed again. (Just to give you an example, C++ .NET is constantly changing the syntax so much that you need to think hard before you refactor some older version of .NET.) So what is the problem with IOC? The problem is in resolving dependencies. The logic for resolving is commonly hidden in the IOC2 itself, written maybe in uncommon way that you need to learn and maintain. Will your third-party product be there in 5 years? Microsoft's was not.

"We know how" syndrome is written all over the place regarding IOC2. This is similar to automation testing. Fancy term and perfect solution at first glance, you simply put all your tests to execute over night and see the results in the morning. It is really painful to explain company after company what automated testing really means. Automated testing is definitely not a quick way of reducing the number of bugs which you can introduce overnight to increase the quality of your product. But, fashion is making that notion annoyingly dominant. IOC2 suffers the same syndrome. It is believed that you need to implement it in order your software to be good. EvErY recent interview I was asked if I am implementing IOC2 and automation. That is a sign of fashion: the company had some part of code written in MFC they will not abandon.

You need to learn IOC2 as any other concept in software. The decision if IOC2 needs to be used is within the team and the company. However, at least ALL above arguments must be mentioned before the decision is made. Only if you see that plus side outweighs negative side, you can make a positive decision.

There is nothing wrong with IOC2 except that it does solve only the problems it solves and introduces the problems it introduces. Nothing else. However, going against the fashion is very difficult, they have sweat mouth, the followers of anything. It is strange how none of them is there when the problem with their fanciness becomes apparent. Many concepts in software industry have been defended because they create profit, books are written, conferences held, new products made. That is fashion, usually short lived. As soon as people find something else they abandon it completely. IOC2 is useful but it shows the same signs as many other vanished concepts I have seen. I do not know if it will survive. There is no rule for that. You think if it is useful, it will survive. No, it does not go that way. One big rich company is enough and the concept can die within few weeks. We'll see. NHibernate survived, EF came second. Maybe IOC2 will survive too. Do not forget that most concepts in software development are about nothing special, they are very logical, simple and obvious, and sometimes it is more difficult to remember the current naming convention than to understand the concept itself. Does the knowledge of IOC2 make a developer a better developer? No, because if a developer was not able to come up with a concept similar in nature to IOC2 then it will be difficult for him or her to understand which problem IOC2 is solving, using it will look artificial and he or she may start using it for sake of being some sort of politically correct.