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Comment by rootlocus | Hacker News Reader

Between duck-typing languages like python and javascript and the minefiled that is C++, I think Java and C# fit a pretty nice sweet-spot. Java absolutely has "just data", they're mostly used for DTOs and database Entities, with tools like lombok @Data and `records` being some nice mechanisms of implementing them.

Inheritance, when used for implementing is-a relationship, is a pretty powerful tool. If you're surprised by overriding, maybe instead of complaining about `Parent parent = new Child()` examples, try to see a `Writer writer = new PdfWriter()`. Are you still surprised that `writer.write(document)` generates a pdf?

There are absolutely horrible ways of designing code in Java, but that can be said about any language.

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> Between duck-typing languages like python and javascript and the minefiled that is C++, I think Java and C# fit a pretty nice sweet-spot.

Imagine where we would be if an actually good way of doing type systems had been invented in the 1970s and there was a whole family of languages that followed that approach. Oh wait.

> Java absolutely has "just data", they're mostly used for DTOs and database Entities, with tools like lombok @Data and `records` being some nice mechanisms of implementing them.

The fact that you have to step outside the language with @Data rather proves the point. And while Java now has a "record" keyword, they're still reference types, with turning them into actual values being something that's supposedly coming Real Soon Now for 10+ years.

> Inheritance, when used for implementing is-a relationship, is a pretty powerful tool. If you're surprised by overriding, maybe instead of complaining about `Parent parent = new Child()` examples, try to see a `Writer writer = new PdfWriter()`. Are you still surprised that `writer.write(document)` generates a pdf?

Inheritance is a conflation of 3 useful features (interfaces, composition, and delegation) that's a lot less useful than the sum of its parts. Better languages separate these out properly. (And, credit where it's due, Java made a positive step in normalizing the separation of interfaces from the other parts of inheritance).

> There are absolutely horrible ways of designing code in Java, but that can be said about any language.

That's a cop-out. No language completely eliminates bad code, but there are better and worse languages.

> The fact that you have to step outside the language with @Data rather proves the point.

You can trivially write a class with public fields without using lombok, you wont get some cookie cutter logic for hashCode and equals, but often you don't need it and with mutable data you may not even want it.

So how would you model a GUI framework’s Node type in (I assume ML/Haskell’s type system is what you mean)? Inheritance is rarely the answer, but it is more than the sum of its parts, and in the rare case it is needed, you really can’t go around that.

> So how would you model a GUI framework’s Node type in (I assume ML/Haskell’s type system is what you mean)?

You'll have to be more specific.

> Inheritance is rarely the answer, but it is more than the sum of its parts, and in the rare case it is needed, you really can’t go around that.

Disagree. If you have the individual parts - interfaces, composition, and delegation - then you can do everything that you can do with inheritance, and you can usually do better since most of the time you only need one or two of the three.

> 1970s

I wonder what fraction of the HN readership gets this joke ...

That's a good point. But IME, when people complain about inheritance, they're primarily talking about implementation inheritance.

Interface inheritance, used for polymorphism like in your example, is still considered a good practice and is not really criticized as much (an exception is when it is "abused" for other reasons, like in codebases that have one interface for every class, even without polymorphism).

Eh, the meme has gotten so strong that I now see people say that subtyping in general is bad. It has escaped the gravity of concrete criticisms of implementation inheritance and morphed into a general “oop bad” thought system.

This is an uncharitable interpretation of the criticism. Several other programming paradigms also have subtyping, often more powerful than OOP, so people moving away from OOP are definitely doing some sort of subtyping in their own language and paradigm, unless they're going to some niche language... or Go.

OOP criticism is often centered around two things: inheritance and state hiding via encapsulation. And this criticism often comes also from programmers that use OOP. And IMO it is pretty fair.

GUI widgets are one area where implementation inheritance is the best model.

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