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If Inheritance is so bad, why does everyone use it?

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Re: If Inheritance is so bad, why does everyone use it?

#321

Post by eddd-ddde »

dragonwriter wrote: post #230
eddd-ddde wrote: post #104

Earlier quoted context omitted.

Except inheritance is the premature optimisation of interfaces. Inheritance forces you to define the world in terms of strict tree hierarchies, which is very easy to get wrong. You may even do a great job today, but tomorrow such properties don't hold anymore. Regular composition allows the same functionality without making such strong assumptions on the data you are modelling.

> Inheritance forces you to define the world in terms of strict tree hierarchies, No, it doesn’t. Inheritance is the outcome of deciding to model some part of the problem space with a tree hierarchy (that potentially intersects other such heirarchies). It doesn’t force you to do anything. I suppose if there was a methodology which forced you, as the only modeling method, to exclusively use single inheritance, that wo…

It may not force you directly, but I think it's safe to say that when a language focuses on inheritance (e.g. c++) it does not offer good alternatives (e.g. rust traits). This means that if you want features such as runtime polymorphism, you are _kinda_ forced into inheritance.

Re: If Inheritance is so bad, why does everyone use it?

#322

Post by dragonwriter »

caseysoftware wrote: post #156

The key is "prefer composition to inheritance" and dates back to Gang of Four. The word "prefer" is critical to understand. It just means "usually choose A over B" not "B is never the right answer." Unfortunately, since we - as an industry - like hard and fast rules, we move towards that second explanation and act like inheritance never makes sense. Like any tool, there's a time and place where it is the best tool, o…

“Prefer A over B” rules usually are problematic because what they usually mean is:

(1) There is a concrete set of cases where A is better than B. (2) But, there is also a concrete set of cases where B is better than A. (3) And, either (a) the cases where A is better than B are more common than the reverse or at least (b) people in the environment where the advice is developed are currently choosing B in cases where A is significantly better.

But, critically, “prefer A over B” does not communicate the set of cases where A is better than B or vice versa, so it tends to lead to the conditions where “prefer B over A” becomes the advice based on (1) and (2) being unchanged but (3)(b) working in the opposite direction.

Re: If Inheritance is so bad, why does everyone use it?

#323

Post by dragonwriter »

cogman10 wrote: post #166
caseysoftware wrote: post #156

The key is "prefer composition to inheritance" and dates back to Gang of Four. The word "prefer" is critical to understand. It just means "usually choose A over B" not "B is never the right answer." Unfortunately, since we - as an industry - like hard and fast rules, we move towards that second explanation and act like inheritance never makes sense. Like any tool, there's a time and place where it is the best tool, o…

I agree with this sentiment but I also must say that the time's I've needed inheritance have been few and far between. I have seen really good examples where it works really well (UX is pretty common, but I've also seen really clean cases like data structures with complex interfaces and a simple abstract class). Where I think inheritance works best is when the state in base classes is limited and the interface is qui…

> I agree with this sentiment but I also must say that the time’s I’ve needed inheritance have been few and far between.

You never strictly need inheritance, but strict need isn’t the criteria for whether something is a good solution (otherwise the fact that most things in programming can be done multiple ways would mean that almost nothing is ever a good solution, since there is almost always an alternative route to the same result.)

Re: If Inheritance is so bad, why does everyone use it?

#324

Post by TheBigSalad »

fransje26 wrote: post #315
caseysoftware wrote: post #156

The key is "prefer composition to inheritance" and dates back to Gang of Four. The word "prefer" is critical to understand. It just means "usually choose A over B" not "B is never the right answer." Unfortunately, since we - as an industry - like hard and fast rules, we move towards that second explanation and act like inheritance never makes sense. Like any tool, there's a time and place where it is the best tool, o…

Would you happen to know any good literature with clear composition examples vs inheritance? The C++ and Python code I see daily is fully inheritance focused, and I would like to understand how it could be done differently (or better) starting from a perspective I understand.

https://gameprogrammingpatterns.com/component.html

Re: If Inheritance is so bad, why does everyone use it?

#325

Post by TheBigSalad »

lucasyvas wrote: post #317

There is no valid use case I've ever seen where inheritance was better than composition (that does not mean a use case does not exist, but evidence is mounting against it). I would say it's used because every language made a poor decision by building that in as the way to encapsulate reusable logic. i.e., a mistake. Some APIs may expose themselves as requiring you extend a base class, and in that case you might as we…

Composition implies a level of complexity. There may be a near infinite number of permutations of things that can be combined. If in reality there are only a fixed set of variations, inheritance may model your system in a tighter way. The benefit can be simplicity.

Re: If Inheritance is so bad, why does everyone use it?

#326

Post by TheBigSalad »

v1sea wrote: post #33

The article has a nice history review of inheritance, but it would have been useful for there to be some concrete examples. The worst example of inheritance I've ever found is in java Minecraft's mobs[0]. It is very deep in some places and has numerous examples of sub classes not fully implementing their parent interfaces. Example 1: Donkey[1] Donkey > Chested_Horse > Abstract Horse > Animal > Ageable Mob > Pathfinde…

Jesus, that's insane! The rule of inheritance is no more than 3 levels deep. 3!!

Re: If Inheritance is so bad, why does everyone use it?

#327

Post by seanwilson »

skydhash wrote: post #306
seanwilson wrote: post #301

Earlier quoted context omitted.

> It's because people don't understand cascade we end up with pages that have text in 18 different font sizes. Variables and/or utility classes mostly solve this so not sure how it's related. > Since then we've got more tools to control cascade: layers, scopes, inherit/initial/revert/revert-layer/unset for every property, etc. But people still insist on inline styling. I get it, it's much simpler. But they will keep…

Cascading does help. When you want to design a document. If you want an application like interface or the same constraints as a magazine page, cascading is the wrong tool for the job. Design tools don’t use it. Layout engines for GUI don’t use it. Flex and Grid is far from the constraints based interface builder in iOS.

> Cascading does help. When you want to design a document. If you want an application like interface or the same constraints as a magazine page, cascading is the wrong tool for the job.

I agree. This sounds like saying cascading helps in simple cases but when it gets more complex it doesn't help.

I don't think anyone really has a big problem writing maintainable CSS for a document. It works fine there. Most CSS methodologies (like BEM) and frameworks (like Bootstrap, Tailwind) are there to help write maintainable CSS code for complex non-document web designs, where a big part of that is taming cascading.

I think a lot of pushback against approaches like Tailwind and JS frameworks are from people that are mostly styling documents. Complex landing pages and UIs are where the real headaches are.

Re: If Inheritance is so bad, why does everyone use it?

#328

Post by TheBigSalad »

arethuza wrote: post #48
bigstrat2003 wrote: post #28

I don't think inheritance is bad at all. It is very often the easiest way by far to model a problem. Sure, it's not perfect, but I think it is wildly overhated by a vocal minority.

Have you ever seen wildly over-architected OO code where everything seems to be an abstract class and it seems impossible to find out where stuff actually happens? Inheritance is like a lot specialised tools - it can be useful in some situations but I think those are rarer than supporters might thing. Completely refusing to use inheritance and always using inheritance both seem like extreme views that should be avoid…

I've seen that same problem sans a deep inheritance hierarchy.

Re: If Inheritance is so bad, why does everyone use it?

#329

Post by butlike »

echelon wrote: post #313
quaunaut wrote: post #217

Earlier quoted context omitted.

I'd be ready to agree if I could be pointed at a time that inheritance actually carries a real benefit- a time you would choose it over composition, if composition is available.

There is no benefit to the "tree of life" single inheritance [1]. What you want to reach for to achieve compositional behavior or polymorphism are type classes, traits, and interfaces. They attach methods to data without the silly "Cat is an Animal, Dog is an Animal" cladistic design buffoonery. There's nothing wrong with OO, except for inheritance-based OO. [1] Don't get me started on multiple inheritance. Instead o…

What about a situation where you have an ECS, and if it has say, LifeComponent(), ReproductionComponent(), it can be identified as an Organism (as opposed to say a Crate). Now, you can have inheritance off of that, a composition can be identified as an Orangutan, or a Human, but only if it was an Organism. The Organism is basically a memoization of Life and Reproduction components on the Orangutan.

Now, A human can create a child, but only if the parent object was a "Human." Am I thinking about this in the wrong way?

Re: If Inheritance is so bad, why does everyone use it?

#330

Post by chuckadams »

GendingMachine wrote: post #258

As a programmer with likely less experience than most of these commenters, the main question that always feels under addressed in these kinds of posts is that of code deduplication. Most specifically, often when encountering a situation in which I have two slightly different classes/types that need to be polymorphic with each other, all the standard non-inheritance based approaches seem to require a lot of outright i…

Typescript is best when you don't use `class` or `this` at all, but instead return object literals of static closures. In other words, more like this:

    function makeCounter(initial = 0) {
        let count = initial;
        function get() { return count }
        function inc() { count += 1 }
        function dec() { count -= 1 } 
        return {get, inc, dec}
     }

      // works just like a normal object
      const ctr1 = makeCounter(); 
      ctr1.inc()

      // but this works too.  try doing this with a class instance.
      const {get, inc} = makeCounter() 
      inc()
This is the typical style of most VueJS code (though it would replace count with a ref and probably call the function `useCounter`). TypeScript is smart enough that it can infer interfaces and even classes from such literals should you go that way, full support for substitutability checking and all.
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