extend a class, implement an interface

Posted Aug 11, 2025 13:38 UTC (Mon) by Replaced_by_AI (guest, #178731)
In reply to: extend a class, implement an interface by paulj
Parent article: Go and Rust — objects without class

It's valid, but the "inheritance concept" in object-oriented programming is limited to classes/objects usage.

Although an interface can also be "inherited" and "inherit", it's not the same as the OO concept, but the word meaning instead.

extend a class, implement an interface

Posted Aug 11, 2025 14:12 UTC (Mon) by paulj (subscriber, #341) [Link]

Almost immediately after the sentence I quoted from the article, Neil mentions interfaces as something that 'inheritance' might apply to:

> The thing is typically a "class", but sometimes an "interface" or even (in prototype inheritance) an "object" that borrows some behavior and state from some other "prototypical" object.

So I brought in 'implements' as a clarifying term precisely because the article itself refers to interfaces. Given the situations the _article considers_ I think 'extends' and 'implements' are the better terms for those situations (which explicitly includes interfaces). I would agree with Neil that, in general understanding, 'inheritance' is not well defined. And this may well be because general software engineers are just unfamiliar with the original precise definitions in founding use or in the literature - but in such situations, we just need to come up with better terminology (and do a better job of 'guarding' their meaning).

The article also misses out on clarifying the rules of typing and sub-typing. These are well-explored in the literature, and there are some very good "rules" that programmers should be familiar with, that can help them avoid mistakes (and some languages can check for them, in at least some cases, if not all). E.g., Liskov's Substitution Principle. (I see another comment has also made that point).