[codazoda]

My first question was, where does “inventory.GetOil()” come from. Is this just a package that wasn’t mentioned? Not being a Go expert, are packages typically global like this? Would that be a good way to implement this function/method (in a package that then becomes available everywhere in main() as opposed to passing it)?

Ah, well, maybe I missed the point entirely.

[eyelidlessness]

I don’t write Go, so I’m similarly not qualified to address how this particular implementation satisfies the dependency. But my hunch is that it’s implicitly an import of a singleton. Which is basically a global, but a fairly common Java-ish pattern for encapsulation of shared dependencies.

It’s not even a terrible pattern if you’ve already accepted shared dependencies as a thing (which you have to do in reality), but it’s much easier to reason about if you isolate them to something that provides explicit dependencies where your logic happens.

[macintux]

After writing almost entirely functional code for the last 10 years, I find it really hard to read and reason about anything that looks like this.

[bedobi]

Totally agree, commented something similar. Both the before and after code shown is impossible to reason about magic. The idea that programming interfaces should be good is good, but this example isn't the best IMO.