I guess I'm a little bit too long already in the functional/data-driven world (after being a decade in OO languages (IMO too long...)). In OOP you may need a separate term for that.

But I think it' just not really necessary in functional programming, it's just another parameter when calling a function, that may be a somewhat type-constrained generic (for testing e.g. with a mock implementation).

I mean function parameters are somewhat dependencies anyway, so should I call all my parameters now dependencies and invocation "injection"?

[–] [email protected] 2 points 1 year ago (1 children)

Thought you were OP for a second there, as they were talking about composability. Whether it's dependency injection or not depends on what shape your parameters take. If you're doing functional programming and you're passing handlers and connections etc. as params, that's dependency injection. If you're only passing strings and objects and such and the function has to do a bunch of logic to decide how to handle its params, that's not dependency injection.

[–] [email protected] 1 points 1 year ago

I think the main reason OOP has a well-known term and pattern for dependency injection is to differentiate these two (out of multiple) options:

the constructor of my object creates other objects it depends on itself
I construct the dependencies of my object elsewhere and pass them in to the constructor and use an interface to make it easy to swap behaviour

However, this becomes less of a pattern in functional programming as you wouldn't make such objects to begin with. In FP, you pass all parameters where a function is invoked, and DI just becomes using generic parameters. You wouldn't instantiate a dependency on each function call after all.

As this is such a minor change, it's not really talked about much and it's not really a pattern,