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0 pointsinsanitybit2y ago0 comments

Inheritance provides "is a" relationships between classes. At a time when people would spend months designing their software upfront, building big diagrams of classes, etc, this was not so bad. You'd have a very clean system design that maps directly to your class design.

The problem is when things change. A simple example - you build a classification of all life and it is built upon the idea that everything "is a" plant or animal. And then one day it turns out there are fungi. This is not a fun situation to deal with and inheritance makes it a lot harder because the "is a" relationship is driving a ton of your logic.

IDK I don't want to get to into it beyond that, many people have written quite a lot on the topic.

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kaba02y ago

> you build a classification of all life and it is built upon the idea that everything "is a" plant or animal

With all due respect, this and similar examples are just plain wrong, and I really can't take anyone seriously when that example is used. The point of programming, and its abstractions is to help you complete a task, and make the implementation maintainable and easy to reason about. I think grabbing the "is a" part is fundamentally bad -- there is no point in creating a taxonomy in and of itself, this is no database for that data. Inheritance sometimes is the correct abstraction and while it is definitely overused, when it's correctly applied there isn't really another abstraction that would fit better. E.g. see a graphics library's Node class as the stereotypical correct application.

insanitybitOP2y ago

I think your post can be broken down into two main points.

1. That my point is bad for some reason

2. That inheritance is sometimes a great tool

We agree on (2). Inheritance is pretty amazing, even if I think that it's ultimately a terrible feature to build so ingrained into a language and to expand in power to such a degree.

As for (1), I don't really get your point. Abstractions help you complete a task - ok. Abstractions are to help you reason about stuff - ok. Something about "is a" being bad? None of that really explains why my example demonstrates the problems you run into when you try to build a classification of values using inheritance. But I also said that I wasn't going to really try to explain much, it's been written about plenty.

bb882y ago

> This is not a fun situation to deal with and inheritance makes it a lot harder because the "is a" relationship is driving a ton of your logic.

Judicious OOP design allows others to change behavior based upon needs that perhaps the original coder never thought of.

I would not call most Java OOP design judicious. The control in Java is owned by the library writers and the language devs -- not the people using it.

akkad332y ago

What is a language with judicious oop design? Asking to know

bb882y ago

I tend to be fond of Python OOP styles.

wayfinder2y ago

This problem is partly a type system limitation however.

In a more flexible type system with union types and other magical features, your example problem would be less of an issue.

However Java has an extremely limited type system so there is no middle ground between composition and inheritance. Once you choose one way, there is no “middle step” to migrate over.

kaba02y ago

Union types are very rare (scala, typescript are the notable ones I can think of that implement it), most other languages only have sum types (which includes java as well, see sealed interface/classes), where you have to create each unique set of types you want to use separately, wrapping each option into a marker type basically.

inglor_cz2y ago

In cases of refactoring, inheritance seriously sucks.

But it is quite advantageous when, as you say, your model is well thought out and stable.

j / k navigate · click thread line to collapse

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kaba02y ago

> you build a classification of all life and it is built upon the idea that everything "is a" plant or animal

insanitybitOP2y ago

I think your post can be broken down into two main points.

1. That my point is bad for some reason

2. That inheritance is sometimes a great tool

We agree on (2). Inheritance is pretty amazing, even if I think that it's ultimately a terrible feature to build so ingrained into a language and to expand in power to such a degree.

bb882y ago

> This is not a fun situation to deal with and inheritance makes it a lot harder because the "is a" relationship is driving a ton of your logic.

Judicious OOP design allows others to change behavior based upon needs that perhaps the original coder never thought of.

I would not call most Java OOP design judicious. The control in Java is owned by the library writers and the language devs -- not the people using it.

akkad332y ago

What is a language with judicious oop design? Asking to know

bb882y ago

I tend to be fond of Python OOP styles.

wayfinder2y ago

This problem is partly a type system limitation however.

In a more flexible type system with union types and other magical features, your example problem would be less of an issue.

However Java has an extremely limited type system so there is no middle ground between composition and inheritance. Once you choose one way, there is no “middle step” to migrate over.

kaba02y ago

inglor_cz2y ago

In cases of refactoring, inheritance seriously sucks.

But it is quite advantageous when, as you say, your model is well thought out and stable.

j / k navigate · click thread line to collapse