You can get Liskov from interfaces too. I rarely (like once in a career) need inheritance.
When did people favor composition over inheritance?
11–20 of 218 posts
Re: When did people favor composition over inheritance?
#12i think inheritance got a bad name due to abuse of multiple inheritance and overly fragile base classes in c++ (and maybe java) codebases of the 90s and early 00s.
it's mentally satisfying to create a beautiful class hierarchy that perfectly compresses the logic with no repetition, but i think long term readability, maintainability and extensibility are much better when inheritance is avoided in favor of flat interfaces. (also easier to turn into rpcs as all the overcomplicated object rpc things of the 90s were put to bed).
Re: When did people favor composition over inheritance?
#13Arguably the answer is “When Barbara Liskov invented CLU”. It literally didn’t support inheritance, just implementation of interface and here we have her explaining 15 odd years later why she was right the first time. I used to do a talk about Liskov that included the joke “CLU didn’t support object inheritance. The reason for this is that Barbara Liskov was smarter than Bjarne Stroustrup.”
I mean, duh. The spicier take is that Barbara Liskov is smarter than Alan Kay.
Re: When did people favor composition over inheritance?
#14Arguably the answer is “When Barbara Liskov invented CLU”. It literally didn’t support inheritance, just implementation of interface and here we have her explaining 15 odd years later why she was right the first time. I used to do a talk about Liskov that included the joke “CLU didn’t support object inheritance. The reason for this is that Barbara Liskov was smarter than Bjarne Stroustrup.”
There is a reason C++ devs and only C++ devs have nightmares of diamond inheritance. Oh the damage that language has done to a generation, but at least it is largely passed us now.
I'm spoiled by Python's incredibly sane inheritance and I always have to keep in mind that inheritance is a very different beast in other languages.
Re: When did people favor composition over inheritance?
#15[deleted]
Re: When did people favor composition over inheritance?
#16i think inheritance got a bad name due to abuse of multiple inheritance and overly fragile base classes in c++ (and maybe java) codebases of the 90s and early 00s. it's mentally satisfying to create a beautiful class hierarchy that perfectly compresses the logic with no repetition, but i think long term readability, maintainability and extensibility are much better when inheritance is avoided in favor of flat interfa…
Rpcs really can't be understated in terms of the effect they had on classes and inheritance.
While in theory it should be straightforward to ship instance state over a wire, in practice most languages have no built-in support for it (or the support is extremely poor in the general case; I remember my first experiments with trying to ship raw Java objects over the wire using the standard library tools back in the early 2000s, and boy was that incredibly inefficient). Additionally, the ability to attach arbitrary methods to instances in some languages really complicates the story, and I think fundamentally people are coming around to the idea that the wire itself is something you have to be able to inspect and debug so being able to understand the structure in transit on the wire is extremely important.
Classes and their inheritance rules make exactly the wrong things implicit for this use case.
Re: When did people favor composition over inheritance?
#17If it's a car with extra wheels, do inheritance.
If you're adding a device for navigation that could be used by other things, go for composition.
Re: When did people favor composition over inheritance?
#18Yeah inheritance is just not the point of OO. It’s fine but it’s not what’s really useful.
Re: When did people favor composition over inheritance?
#19Arguably the answer is “When Barbara Liskov invented CLU”. It literally didn’t support inheritance, just implementation of interface and here we have her explaining 15 odd years later why she was right the first time. I used to do a talk about Liskov that included the joke “CLU didn’t support object inheritance. The reason for this is that Barbara Liskov was smarter than Bjarne Stroustrup.”
There is a reason C++ devs and only C++ devs have nightmares of diamond inheritance. Oh the damage that language has done to a generation, but at least it is largely passed us now.
Diamond inheritance is its own special kind of hell, but “protected virtual” members of java and c# are the “evil at scale” that’s still with us today. An easy pattern that leads to combinatorial explosion beyond the atoms in the universe. Trivially.
People need to look at a playing deck. 52 cards, and you get 8×10^67 possible orders of the deck. Don’t replicate this in code.
Re: When did people favor composition over inheritance?
#20When someone realized that the inheritance glass castle is doomed to always get shattered upon contact with the real world.
Inheritance might be OK for formally finite domains but I can’t envision other cases where it should be favored.