Composition over Inheritance
Always / sometimes / never?
Rarely are there 100% certainties in best practices. They’re largely true, but we shouldn’t get lost in them if they somehow lower the bar for the quality of the codebase.
I would take a good inheritance all day. Otoh , I suck at music so no compositions happening anytime soon.
Mostly. Way easier to unit test.
In C++, public inheritance should only be used when you want to establish an "is-a" relationship (substitutability). It's a very strong relationship. In all other cases you should use composition to import desired functionality. (In some cases, private inheritance can be used for composition.)
Composition is a “has a” relationship and inheritance is a “is a” relationship. Here’s an easy way to figure out whether you should use one or the other. If I inherit the class will I be writing less code ? Inheritance saves you variable duplication because lone and behold... the parent contains those variables. If I want to extend a function and be able to decorate the parent function. Composition would it make sense to compose this object and use it else where ? To reduce coding more ? These key points are how you basically write oop code.
The answer to any sort of question like this is “it depends”. There are rarely any one-size-fits-all solutions