4 ms·

> The reason is that inheritance is almost always a bad idea in practice. It's just slightly too strong of a statement. I'm working in a very large Spring cod

> The reason is that inheritance is almost always a bad idea in practice. It's just slightly too strong of a statement. I'm working in a very large Spring codebase right now, with a lot of horrible inheritance abuse (seriously, every component extended common hierarchy of classes that pulled in a ton of behavior). I suspect part of the reason is the Spring context got out of control, and the easiest way to reliably "inject" behavior is by subclassing. Terrible. On the other hand, inheritance is sometimes the most elegant solution to a problem. I've done this at multiple companies: Payment + PayPalPayment + StripePayment Sometimes you have data (not just behavior!) that genuinely follows an IS-A relationship, and you want more than just interface polymorphism. Yes you can model this with composition, but the end result ends up being more complex and uglier. It doesn't have to be all one or the other. But I agree, it should be mostly composition.

WesolyKubeczek 1y ago
There used to be times when language-level composition did not exist, so inheritance was practically all you had. There used to be ugly hacks to implement mix-ins, for example, in PHP (first versions of Symfony used them and did their best to make them not ugly, but they had to devote a whole chapter on how to do them right anyway). I suspect a lot of contention comes from those times — and from the fact that even when you can do better, many folks still have the muscle memory wired to "if inheritance is the only tool you have, everything looks like a subclass". I like languages where I can have both, and where the language authors are not trying to preach at me.
roguecoder 1y ago
That is a great example! Abstraction is most useful when it captures the way several things are more-specific versions of a more general thing. At that point it's not just about the functionality: it communicates to the reader. Anyone coming in can now easily answer the question, "what kinds of payments exist?"

WesolyKubeczek 1y ago

There used to be times when language-level composition did not exist, so inheritance was practically all you had. There used to be ugly hacks to implement mix-ins, for example, in PHP (first versions of Symfony used them and did their best to make them not ugly, but they had to devote a whole chapter on how to do them right anyway). I suspect a lot of contention comes from those times — and from the fact that even when you can do better, many folks still have the muscle memory wired to "if inheritance is the only tool you have, everything looks like a subclass". I like languages where I can have both, and where the language authors are not trying to preach at me.

roguecoder 1y ago

That is a great example! Abstraction is most useful when it captures the way several things are more-specific versions of a more general thing. At that point it's not just about the functionality: it communicates to the reader. Anyone coming in can now easily answer the question, "what kinds of payments exist?"