Re: [RFC][Draft] Sealed Classes

Forwarding to the list, and answering: On Wed, Apr 28, 2021 at 9:51 AM Tony Marston <tonymarston@hotmail.com> wrote: > On 27/04/2021 17:22, Guilliam Xavier wrote: > > On Sat, Apr 24, 2021 at 12:55 PM Saif Eddin Gmati <azjezz@protonmail.com > > > > wrote: > > > > > > To me the first sentence of the RFC is debatable: > > > >> The purpose of inheritance is code reuse, for when you have a class that > >> shares common functionality, and you want others to be able to extend it > >> and make use of this functionality in their own class. > > > > That sounds like [abstract] base classes, which certainly permit that, > but > > I wouldn't state that "the purpose" of [designing] class hierarchies is > > "code reuse", which can also (better?) be achieved with traits or even > > simply composition > > I completely disagree that the first sentence of that RFC is debatable > as I consider it to be totally accurate. When you use inheritance via > the 'extends' keyword then every method in the superclass is shared by > the subclass. In the subclass you have the option to override the > implementation of any method in the superclass, or you can add new > methods of your own. But does that necessarily mean that "The purpose of inheritance is code reuse"? This superclass may be abstract, but it need not > be. The methods it contains may be abstract, but they need not be. > I didn't say that they need (the brackets meant "optionally"). And does it really matter actually? > According to the Gang of Four the way to avoid the problems caused by > the overuse of inheritance is to only inherit from an abstract class, > which is precise what I do. I am famous for having an abstract table > class in my framework which contains hundreds of methods and thousands > of lines of code, and because each of my 400 concrete table classes > inherits from the same abstract table class that is a LOT of code which > is shared. This abstract table class also allows me to use the Template > Method Pattern (which is mentioned in the Gang of Four book) so that all > the invariant methods are defined in the abstract class which means that > each subclass need only contain the variable "hook" methods for which it > needs to provide an implementation. > Well, PHP is flexible. I have seen many combinations of (one or several of) interface, [abstract] class, trait, composition... depending on the context. > When you say that code reuse can be better achieved with traits or > object composition I have to disagree. I said "also (better?)", not just "better". But one can think "no" to "better?" ;) Object composition is used only > by those idiots who overuse inheritance, :/ and there is no evidence that > traits are "better" than inheritance. > By the way, is there evidence to the contrary? (genuine question) > Inheritance, when used sensibly, is still the best way to share code. > Your opinion, maybe not unanimity (nor absolute truth). > Regards, > > Tony Marston > > Regards, -- Guilliam Xavier