I think the biggest mistake was to teach inheritance as a main feature of OOP. I have done some stuff with inheritance but it was very specialized and it would have been fine without inheritance.
It was a common pattern, back then. We’d pass around structs, and have a small library of functions that accessed/modified the data in these structs.
If you wanted, you could add function pointers to the structs. You could add “polymorphism,” by overwriting these pointers, but it was messy.
That said, inheritance can be very useful, in some cases, like improving DRY. I don’t like to take absolute stances, so much, these days.
Its not very intuitive used that way.
Do people honestly think other languages don't do whatever definition OOP has today? Encapsulation & polymorphism? Message-passing & late-binding?
Inheritance is the one thing that the other languages took a look at and said 'nope' to.
(Also, the OOP texts say to prefer composition anyway)
It is very difficult to tell whether this is a definitional problem - people believe any kind of encapsulation is OOP - or if some people can't wrap their heads around how to do encapsulation without message passing and the rest.
What they don’t get with protocols, though, is polymorphism. I think a lot of folks confuse them.
I wrote about an odd bug that I encountered, from protocol defaults: https://littlegreenviper.com/the-curious-case-of-the-protoco...