> What really frustrates me is that almost none of the OOP instruction I've encountered ever showed these kinds of real, practical examples. They always over-emphasize harmful inheritance-based approaches and never really explain composition.

So true. The canonical example used by OO pundits is often a "Person". A Person can be either a Contractor or an Employee (inheritance).

Having spent a lifetime in HR systems, there really couldn't be a worse example. It turns out that people may become contractors or employees, and then change back again, leaving the company and then returning. Some people may even hold the role of contractor and employee contemporaneously. Any crazy shit is true for humans. Instead of using simple OO classes to model people, IRL you end up with many, many tables that capture their lifecycle.

Good OO candidates/examples are usually non real worl things. Window managers and windows. Progamming concepts. That kind of thing, where the rules are simple and point in time.

> I didn't fully grok OOP until I saw how composition and dynamic dispatch can be used in real code to create abstractions and flexibly swap out different implementations for your interfaces.

> You could build a chatbot that supports Discord, Slack, and IRC dynamically at runtime...

As a counter-point, OOP isn't necessary for dynamic dispatch.

None of these dynamic features you describe are necessarily any harder in non-OOP languages — or easier in OOP languages.

You can do the same kind of dynamic dispatch in Elixir, Go, etc.

OOP really is a preference, not a differentiator.

Source: I cut my teeth on OOP and used it for many years. Been using Elixir for the last half a decade, and have zero loss of ability to do things like this.

For me, the issue was that OOP in an academic context was always toy examples. OK, Dog and Cat are Animal that can MakeNoise, Eat, and HaveFur (except sometimes not). Yeah, I get it. It's a ridiculous amount of boilerplate compared to just throwing some functions in and getting it done.

The issue was that anything they taught had to be dumbed down to the point to fit in a classroom and they basically stopped there. We also never wrote code that would be looked at by more than one person. I didn't "get it" until I spent years in a real job, with systems complex enough for this to matter, and practical examples like Dependency Inversion etc as you say. There was also a complete lack of Composition and (at the time I did it) multiple-inheritance which is a bit more controversial these days.

Our traditional Comp Sci course also worked on a variety of languages but nearly zero UI or web programming back then, which are both natural fits for OOP that we largely ignored.

Examples totally do suck.

A class Animal is inherited by Dog class that barks. That's like the total opposite of what any practical example can be and people confuse how that's even useful.