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0 pointsitronitron3y ago0 comments

Dependency injection is one of those technical terms that are made up to describe something that has been done for decades but with a new name because the creators of the new term don't have much experience and/or they want to gain notoriety for creating a new programming technique.

If you've ever written a constructor for a class that has arguments (within the constructor signature) that are used by the instance of the class when instantiated then you have done dependency injection, or put more simply 'passing stuff in' which was eloquently stated in another comment on this thread.

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kagakuninja3y ago

I believe the term Dependency Injection was coined by Martin Fowler, as the meaning of the pattern name Inversion of Control is less obvious. I'm going to assume that Martin Fowler has quite a bit of experience, although you might accuse him of wanting to gain notoriety...

In any case, DI is not at all a new trendy term. Inversion of Control dates back to the gang of 4 patterns book from the '90s. Yes, constructor parameters are one way to implement DI, but not the only one. I'm ambivalent on the whole pattern movement, but they are a great educational tool for novice programmers, and it is good to have some standard terminology for core patterns.

To put it another way, constructor based DI is not simply the use of constructor parameters, it is understanding the OO design principle that side-effecting code should be isolated into objects, rather than just dumping a bunch of DB queries into your functions, like we did back in the stone age.

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