inheritance | Simulation of the effects of inherited wealth

It seems like you are either directly or indirectly (through some other library) depending on Lifecycle 2.5.0-alpha01.

As per this issue:

You need to temporarily add following to your build.gradle:

Parallel Inheritance Hierarchies makes many unnecessary classes and makes code very fragile and tightly coupled. For example, we have class Sportsman and its Goal's.

Assuming that you're talking about the language feature (e.g. interface keyword in Java), as opposed to the general computing term, the purpose of interfaces is polymorphism.

A tool such as interfaces can be abused for other purposes, for example:

• As a way of communicating commonality - this can backfire, because if polymorphism isn't the goal of the design, then the classes which declare implementing the interface are making an unnecessary commitment to implement it. That may cease to be relevant when the commonality is eventually broken, which can happen because the classes aren't used polymorphically.

• As a way of documenting the contract and allowing the class implementation to change - In Java, this is achieved with public/protected methods with Javadoc are the way to document the contract. Some languages don't even have that, and they still document contracts. Of course, this only works if the contract comes in form of function calls (as opposed to e.g. RESTful HTTP APIs), and it only works if you have a rule about what you document, e.g. package boundary; you wouldn't want to create an interface for every class, even if you document the contract for every class.

• To physically hide stuff from the consumer of your interface - this is also about documenting the contract, but if your class has data, or protected methods, and you want to prevent anything outside your package from inheriting, you can expose only an interface. But you can also use final.

Interfaces aren't designed to achieve multiple inheritance; they rather facilitate multiple inheritance only to the extent that is useful for polymorphism; it doesn't really allow you to inherit any fields, and until recently in Java with default methods (so, not by design), not even code.

You would see, in the wild, packages where only one class implements the interface. That doesn't render the interface useless; more implementations may come in the future, and in fact, the package might want to allow callers to offer their own implementation.

One way to solve the issue is by parameterizing the ParentDTO Class with its own children.

https://bugs.ruby-lang.org/issues/9573 shows a similar behavior concerning classes and modules. The bug report was posted on 2014 and was only closed 2020. Based on that report, I've manually confirmed that

• This behavior still appears in ruby 2.7.2p137 (2020-10-01 revision 5445e04352) [x86_64-linux], but
• This behavior no longer appears in ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-linux]

Unfortunately, records don't behave the way you expect them to.

When you declare a record, you get the equality check operator and methods for free.

Your base class just returns true, but when you declare the derived record as a record, you get an equality check method in there as well, that will look like this:

Implicit implementations tend to be more common and more convenient for usage. They are less verbose and any usage of the concrete type will have the implementations of the members exposed. Implicit implementations don't include the name of the interface being implemented before the member name, so the compiler infers this. The members will be exposed as public and will be accessible when the object is cast as the concrete type.

Visit this link for more details https://www.pluralsight.com/guides/distinguish-explicit-and-implicit-interface-implementation-csharp

If you're just going to reuse a property from a superclass but treat it as a narrower type, you should probably use the declare property modifier in the subclass instead of re-declaring the field:

The EXPORTHOW mechanism is only for overriding the metaclass that will be used for package declarators, with the slight extension that EXPORTHOW::DECLARE also performs a grammar tweak that introduces a new package declarator.

While one can call .HOW on a Sub, the result does not relate to the subroutine itself, but rather the metaclass of the Sub type, of which a subroutine is an instance.

Really, EXPORTHOW is an "easy things easy" mechanism (to the degree it's fair to call anything relating to meta-programming easy!) It was also a straightforward thing to provide: the parsing of package declarations was already extremely regular, and the compiler already maintained a mapping table from package keyword to metaclass, so providing a way for a module to replace entries in that table (or add new ones for DECLARE) was barely a few hours of compiler hackery.

Routines are vastly less regular, even if that's only somewhat apparent syntactically. While packages pretty much parse the keyword (class, role, grammar, etc.) and what follows is the very same syntax and semantics for all of them (modulo roles permitting a signature), there are separate parse rules and semantics behind each of sub, method, macro, and rule. Their interaction with the overall compilation process is also rather more involved. The ongoing RakuAST effort is bringing a bit more order to that chaos, and ultimately - when coupled with slangs - will offer a way to introduce new sub-like constructs, as well as to give them semantics.