Dependency Injection is dangerous for your career

DI is generally used to solve one of three problems that are pretty much unique to Java:<p>Passing a function<p>Decoupling initialization from memory allocation (eg. making constructors work) (This problem is also shared by C# before 3.0 but you can kind of get around it by passing a function that does the initialization, or using an anonymous constructor in 3.0 and up)<p>Avoiding the FactoryFactoryFactory pattern where it's all factories all the way down which is a pattern designed to get around the constructor anti-pattern. Because constructors are somehow special and not just a function that returns a specific data-type. So in C# you'll wrap a constructor in a function so it can be passed, and in Java you'll use DI. (eg. Func&#60;String&#62; s = () =&#62; new string())<p>DI is primarily a euphemism for programming in XML or another language that sucks less than Java. Primarily it's a euphemism designed to assage the egos of Java programmers who don't want to admit you can't solve problems elegantly in Java so they move their code to other languages that interact with Java to pretend Java solves more problems than it creates.

Hilarious. :) Some of the other answers are worth reading, too. Specifically, there is a really good one a little lower that is worth reading:<p><a href="http://stackoverflow.com/questions/2407540/what-are-the-downsides-to-using-dependency-injection/2408237#2408237" rel="nofollow">http://stackoverflow.com/questions/2407540/what-are-the-down...</a><p>&#62; The same basic problem you often get with object oriented programming, style rules and just about everything else. It's possible - very common, in fact - to do too much abstraction, and to add too much indirection, and to generally apply good techniques excessively and in the wrong places...[answer continues]

True. But what's even worse for your career is when you learn programming languages that don't need DI frameworks because that kind of clean separation is baked in (like Python) but then most jobs out there are Java :-(

The following is a comment from Frank Atanassow on a LtU discussion about the Curry Howard correspondence:<p>blah blah blah dependency injection blah blah blah (This is a bit off-topic, but it came to mind, so what the hell.) You are correct in your observations that given most programming languages (even those such as Haskell), it is difficult to see exactly how Curry-Howard is useful. I recently stumbled across someone mentioning something called "dependency injection". I didn't know what it was, so I googled (I guess this is lowercase nowadays!) it and read Martin Fowler's article on it. It is a bit on the long side, and I kept waiting for the punch-line; you know, the point at which the author hits you with the insight which justifies the preceding verbosity and the hi-tech-sounding name ("dependency injection" — I can't help but think of "fuel injection", and gleaming motor engine showcases), but it seemed indefinitely postponed. And in the end, it turned out that "dependency injection" just means "abstraction" specifically by parametrization, by update and by what I think amounts to type abstraction plus update. (Apparently these are called — I kid you not — type 3 IoC, type 2 IoC and type 1 IoC...!) To me this all seemed rather obvious and it got me thinking about why it isn't obvious to the author or his readership. In Haskell, if I am given some type B which I need to produce somehow, and I realize that the B-values I need depend on some other values of type A, the first thing I do is write down "f :: A -&#62; B". Then I write down "f a =", and then I start writing stuff after the equals sign until I have what I need. I do that because I know once I have the type that if there is an inhabitant of the type "A -&#62; B" it can be expressed as "\a -&#62; b" for some b, so the "f a =" part is always part of my solution and I will never have to change that unless I want to. So once I've written that down I feel one step closer to my solution. I know that for three reasons. First, because of my experience as a functional programmer. Second, because it is part of the universal property of exponentials ("factors uniquely"), that is, of function types. And third, because by the Curry-Howard correspondence with natural deduction, I can start any proof of A which depends on B by assuming A, that is, adding it as a hypothesis. So, why is it so obscure in Java? I think part of the reason is that in Java you have update, so there are complications and additional solutions. But part of the reason is also that it largely lacks structural typing, and that makes it hard to see that a class('s interface) is a product of exponentials. (With nominal typing, you tend to think of a class by its name, rather than its structure.) You could also blame the syntax of method signatures, which obscure the relationship with exponentials and implication. But is the syntax the cause or just a symptom? (You know what I think about syntax...) If CH could be readily applied to Java, perhaps Java's designers would have chosen a more suggestive syntax. But even if they had decided to stick anyway with C-style syntax, the idea of using abstraction to handle dependencies would have been more obvious.<p>More: <a href="http://lambda-the-ultimate.org/node/1532" rel="nofollow">http://lambda-the-ultimate.org/node/1532</a>

Thats probably one of the funniest stack overflow threads I have read.

Dependency injection separates discovery from dependency. It's neither good nor bad but can be useful as well as abused beyond ad nauseum. End of story.

How can you tell how closely coupled a codebase is when you're in the interview process and not yet an employee?<p>This is the real challenge. I don't think many companies, outside of perhaps small startups, will let you view their code - at your own perusal so you know they aren't just showing off the good stuff - to candidates.

well known fact, game developers use DI like it was 2nd nature to them not matter what computer language they use..<p>..Gaming is Life