Is Inheritance really needed?

Question

I must confess I\'m somewhat of an OOP skeptic. Bad pedagogical and laboral experiences with object orientation didn\'t help. So I converted into a fervent believer in Visua

Answer 1

Not needed, but usefull.

Each language has got its own methods to write less code. OOP sometimes gets convoluted, but I think that is the responsability of the developers, the OOP platform is usefull and sharp when it is well used.

Answer 2

The problem with inheritance is that it conflates the issue of sub-typing (asserting an is-a relationship) and code reuse (e.g., private inheritance is for reuse only).

So, no it's an overloaded word that we don't need. I'd prefer sub-typing (using the 'implements' keyword) and import (kinda like Ruby does it in class definitions)

Answer 3

The GoF (and many others) recommend that you only favor composition over inheritance. If you have a class with a very large API, and you only want to add a very small number of methods to it, leaving the base implementation alone, I would find it inappropriate to use composition. You'd have to re-implement all of the public methods of the encapsulated class to just return their value. This is a waste of time (programmer and CPU) when you can just inherit all of this behavior, and spend your time concentrating on new methods.

So, to answer your question, no you don't absolutely need inheritance. There are, however, many situations where it's the right design choice.

Answer 4

Inheritance is a good thing when the subclass really is the same kind of object as the superclass. E.g. if you're implementing the Active Record pattern, you're attempting to map a class to a table in the database, and instances of the class to a row in the database. Consequently, it is highly likely that your Active Record classes will share a common interface and implementation of methods like: what is the primary key, whether the current instance is persisted, saving the current instance, validating the current instance, executing callbacks upon validation and/or saving, deleting the current instance, running a SQL query, returning the name of the table that the class maps to, etc.

It also seems from how you phrase your question that you're assuming that inheritance is single but not multiple. If we need multiple inheritance, then we have to use interfaces plus composition to pull off the job. To put a fine point about it, Java assumes that implementation inheritance is singular and interface inheritance can be multiple. One need not go this route. E.g. C++ and Ruby permit multiple inheritance for your implementation and your interface. That said, one should use multiple inheritance with caution (i.e. keep your abstract classes virtual and/or stateless).

That said, as you note, there are too many real-life class hierarchies where the subclasses inherit from the superclass out of convenience rather than bearing a true is-a relationship. So it's unsurprising that a change in the superclass will have side-effects on the subclasses.

Answer 5

I agree with everyone else about the necessary/useful distinction.

The reason I like OOP is because it lets me write code that's cleaner and more logically organized. One of the biggest benefits comes from the ability to "factor-up" logic that's common to a number of classes. I could give you concrete examples where OOP has seriously reduced the complexity of my code, but that would be boring for you.

Suffice it to say, I heart OOP.

Answer 6

Absolutely needed? no, But think of lamps. You can create a new lamp from scratch each time you make one, or you can take properties from the original lamp and make all sorts of new styles of lamp that have the same properties as the original, each with their own style.

Or you can make a new lamp from scratch or tell people to look at it a certain way to see the light, or , or, or

Not required, but nice :)