Inheritance is evil!

Read this on Bernie's blog:

"All of the pain caused by inheritance can be traced back to the fact that inheritance forces 'is-a' rather than 'has-a' relationships. If class R2Unit extends Droid, then a R2Unit is-a Droid. If class Jedi contains an instance variable of type Lightsabre, then a Jedi has-a Lightsabre.

The difference between is-a and has-a relationships is well known and a fundamental part of OOAD, but what is less well known is that almost every is-a relationship would be better off re-articulated as a has-a relationship."

I suggest you read the full story, as it's very interesting! Bottom line is that you should be careful using OO inheritance, and use the Strategy pattern instead.

This is an imported post. It was imported from my old blog using an automated tool and may contain formatting errors and/or broken images.